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Growth Factors

Also known as: growth factor, cytokines, conditioned media, topical growth factors

Growth factors are signalling proteins that influence cell behaviour. In skincare they appear as recombinant proteins or complex conditioned-media preparations; topical studies report modest short-term appearance changes, but intact-skin delivery is unproven and human-derived cosmetic ingredients create a current Great Britain compliance concern.

Evidence status

Limited

An independent systematic review covered 33 studies, 1,180 participants and 23 preparations (9 RCTs), finding modest investigator-assessed improvements—median <50% for texture, <35% for fine lines and <20% for overall appearance—while three comparative RCTs found no significant product difference. Manufacturer-linked authorship, single-product designs and mixed co-ingredients limit attribution, and no source shows a marketed intact growth factor (roughly 6 kDa for EGF versus the conventional 500 Da penetration rule) reaching viable epidermis through intact skin. The becaplermin cancer signal arose on open diabetic ulcers and did not persist with follow-up; long-term cosmetic safety remains unstudied.

What growth factors are, and the types available#

Growth factors are signalling proteins that bind receptors and influence cell proliferation, migration, differentiation and matrix activity. Those most often named in skincare include epidermal growth factor (EGF), transforming growth factor beta, vascular endothelial growth factor, keratinocyte growth factor (FGF-7) and platelet-derived growth factor. Several are known to affect collagen biosynthesis directly.[3, 15]i

The category contains materially different preparations:

  • recombinant single proteins, including human-sequence EGF produced in a non-human expression host;
  • human-cell conditioned media, containing a mixture of factors secreted by cultured cells;
  • human-cell lysates, containing material released from disrupted cultured cells;
  • non-human secretions or extracts described as having growth-factor-like activity.

These descriptions do not mean the same thing. “Barley-derived EGF” is recombinant human-like EGF expressed in barley; the plant is the production host rather than the source of a plant growth regulator.[3, 8] Snail secretion filtrate is described as having fibroblast-growth-factor-like activity and is not evidence of human EGF, TGF-beta, VEGF, KGF or PDGF in the product.[12, 11]

Growth factors are also distinct from exosomes. A growth factor is a soluble signalling protein. An exosome is a lipid-bilayer extracellular vesicle that may carry proteins and nucleic acids. Conditioned media can be marketed with language from both categories, but evidence for a growth-factor preparation does not validate an exosome preparation.

Use of growth-factor products in aesthetic practice#

Topical application of a compliant cosmetic sits within skincare practice. The origin and route of the material determine the more important boundaries.

In Great Britain, Annex II of the assimilated Cosmetics Regulation prohibits “cells, tissues or products of human origin” in cosmetic products.[13] Premium products described in the literature have used neonatal-foreskin fibroblast conditioned media, hypoxically cultured human fibroblast media or human fibroblast lysate; one gel was described as containing more than 110 factors, cytokines and soluble matrix proteins secreted by human dermal fibroblasts.[3, 5]

A label naming human fibroblast conditioned media, human adipose stromal cell conditioned media, human fibroblast lysate or comparable human-derived material therefore engages entry 416. No published OPSS or MHRA enforcement guidance applying the entry specifically to this category was located. That uncertainty does not remove the prohibition: the Responsible Person or supplier must be able to demonstrate why the marketed product is compliant before it is applied or retailed in Great Britain.[13, 3, 8]i

Recombinant human-sequence protein expressed in a non-human host does not present the same human-origin issue, but it does not inherit stronger clinical evidence. The reference barley-EGF study was an open-label, uncontrolled study in 29 women, with every participant also using sunscreen and cleanser.[8]

Topical application is not one of the five modalities recognised by the voluntary JCCP register. Delivering material through microneedling sits within its “Skin Rejuvenation – Micro Needling and Peels” modality. A cosmetic safety assessment for surface use does not establish suitability for deliberate delivery through a breached barrier; the exact product and procedure instructions govern.[14]

Contraindications and cautions#

No universal ingredient-level contraindication was established. The practical disqualifiers are regulatory status, product route, an undiagnosed lesion and a presentation that needs medical care.

A human-derived cosmetic whose GB compliance cannot be demonstrated should not be treated as suitable because it is widely sold or described as premium.[13]

An intact-skin cosmetic should not be introduced through microneedling or another breached barrier unless the manufacturer expressly intends and supports that route. Bypassing the barrier changes exposure to a complex protein mixture and moves the act into the governing procedure standards.[14]

Active or recent skin malignancy, a changing lesion or dense untreated actinic damage presents an unresolved theoretical question around mitogenic signalling. No long-term cosmetic-user epidemiology exists. This is a precautionary referral boundary rather than evidence that topical growth factors cause cancer.

Active dermatitis, infection, an open wound outside an authorised medical product pathway or a previous reaction to the formulation also requires treatment to pause and the exact presentation to be assessed.

Clinical uses and the evidence behind them#

Facial appearance and photoageing

The systematic review included 33 studies, 1,180 participants and 23 preparations. Its authors were an academic Queen Mary University of London team with no manufacturer affiliation in the accessible record, but the review's funding and conflict statements could not be retrieved. Investigator-assessed median improvements versus baseline were under 50% for texture, under 35% for fine lines and wrinkles, and under 20% for overall facial appearance.[1]

The ceiling is important. Twenty-four studies were uncontrolled case series, nine were randomised trials and only nine used any placebo or active control. Product composition, additional ingredients and outcome measures varied, so the review supports a modest category signal rather than a transferable effect size for a particular serum.[1]

The best vehicle-controlled human-fibroblast-conditioned-media trial randomised 60 participants and ran for six months, with cleanser and sunscreen in both arms. Its abstract reported endpoints that were either conventionally significant or only “trending” at p≤0.1. The first and corresponding author worked for SkinMedica, which markets the product line.[5]

The foundational histology pilot involved 14 people, no vehicle arm, no randomisation and no blinding. Its 37% result was an increase in Grenz-zone thickness, not a direct 37% collagen increase; epidermal thickness rose 27%. The authors concluded only that the preparation “may” stimulate repair. Funding was not stated, and the proprietary Nouricel-MD base later became the commercial TNS line; the lead investigator was closely associated with its developer, so this is interested-party evidence.[6]

Comparisons between products

The systematic review found that three comparative randomised trials showed no statistically significant difference between treatments. In a 20-person split-face trial, human fibroblast-derived and adipose-mesenchymal-stem-cell-derived formulations both improved from baseline, but did not differ on efficacy, safety or tolerability. Both sides received an active product and there was no vehicle arm. The study was funded by Nuderm, and the senior author consulted for Nuderm and SkinMedica.[1, 7]

The result supports neither superiority nor proof that either active beat a moisturiser. It supports the narrower finding that the two tested formulations did not separate.

Bioengineered EGF

The barley-expressed EGF study reported improvement over three months in 29 women aged 39–75. It was open-label, single-centre, uncontrolled and unblinded, and all participants used sunscreen and cleanser. Funding was not stated, and the senior author has commercial involvement in barley-derived EGF skincare.[8] It is evidence for one recombinant formulation under a combined routine, not for “plant growth factors” as a category.

Snail-derived actives

A 25-person double-blind split-face trial found significant periocular-rhytide improvement on the active snail-secretion side at 12 weeks (p=0.03) and better texture at weeks 8 and 12, persisting two weeks after discontinuation. Participants did not report a significant difference in overall skin quality. Funding and individual conflicts were not stated in the accessible record.[11]

In a separate 50-woman vehicle-controlled trial of snail secretion filtrate plus snail egg extract, both active and vehicle groups improved fine lines and wrinkles. Other measures favoured the active regimen. The trial was funded by Cantabria Labs; one author was an employee and another served on its advisory board.[7, 12]

These are findings for snail-derived formulations described as growth-factor-like. They do not establish the presence or action of human growth factors.

Almost every efficacy and safety source in this field carries a commercial interest — a manufacturer-employed first author, a company-funded trial, a Merz-employed review team, or a review by the founder of the company whose core technology is the molecule under review — so read the literature as an industry brief with independent spot-checks, not as neutral appraisal.[5, 3, 10, 12, 7]

Selecting a growth-factor product#

Selection begins with the source, route, finished formulation and product-specific evidence.

The INCI and supplier documents should identify whether the material is recombinant protein, human-cell conditioned media, human-cell lysate or a non-human secretion. In Great Britain, human origin is a compliance question before it is an efficacy question.[13]

The finished product is the unit of evidence. None of the trials held the vehicle and additional ingredients constant while adding or removing only a growth factor, and three head-to-head trials found no product-level superiority.[1, 7]

Delivery claims also require restraint. Bos and Meinardi’s 500 Dalton rule is an inductive rule of thumb for intact stratum corneum, not an experimental law. Mature EGF is 53 amino acids; TGF-beta-1 is 112, FGF-7 is 163 and PDGF-B is 109, while the common VEGF165 isoform is 165 amino acids. These are folded, multi-kilodalton proteins. A manufacturer-connected review describes growth factors as generally above 15,000 Da and EGF as approximately 6 kDa, around twelve times the conventional threshold.[2][3, 2][15]

Formulation scientists describe low transdermal delivery, material interactions and protein instability in common emulsions as unresolved problems. A growth factor on an ingredient list may not remain intact and bioactive through shelf life, and no independent dose-response or stability threshold was located.[4][4]i

The instructions for the exact product govern application; the evidence does not establish a generic concentration, layering schedule or post-procedure protocol.

Adverse effects and their management#

Short-term tolerability

Across 1,180 participants and 23 preparations, the systematic review reported a low risk of adverse events. Mean treatment duration was about three months. This is reassuring for short-term use and does not establish long-term safety.[1]

Product reactions

Stinging, erythema, itching or dermatitis identifies a response to the finished formulation, which may contain many other ingredients. Progressive or persistent reactions require the product to be stopped and the presentation assessed according to its severity.

Oncological uncertainty

The historical cancer concern came from becaplermin, a prescription recombinant PDGF-BB gel applied to open diabetic ulcers. Extended clinical-trial follow-up produced a cancer RR of 2.8 (95% CI 0.6–12.8), and a single death after three dispensed tubes contributed to a 2008 boxed warning. A later matched-cohort analysis reported cancer mortality RR 5.2 (95% CI 1.7–17.6) through 2003 among people with three or more dispensings.[9, 10]

Longer follow-up was more reassuring: overall cancer incidence HR 1.2 (95% CI 0.7–1.9), overall cancer-mortality RR 1.0 (95% CI 0.5–2.3), and RR 2.4 (95% CI 0.8–7.4) in the narrower group with more than three dispensings. A Veterans Administration cohort of 6,429 users and 6,429 comparators followed for 11 years reported HR 1.04 (95% CI 0.73–1.48) for those receiving at least three tubes versus none. The boxed warning was removed.[9, 10]

These data do not map directly to skincare: they concern one pharmaceutical growth factor, open wounds, pharmacological exposure and an older diabetic population, rather than years of multi-factor cosmetic use on intact facial skin. The 2026 reassuring review was written by two employees/owners and a consultant of a company whose core technology is rhPDGF-BB.[9, 10]i

No epidemiological study was located examining cancer or actinic-keratosis incidence in long-term users of topical cosmetic growth factors.[no source found]

Breached-barrier exposure

Microneedling changes route and potential dose. No safety study addresses delivery of a multi-factor cosmetic mixture through that route. A reaction or suspected infection follows the microneedling complication pathway and the product’s own instructions, not an improvised growth-factor protocol.

Referral and scope boundaries#

Referral is indicated for a changing or undiagnosed lesion, active or recent skin malignancy, dense actinic damage needing assessment, a non-healing wound, infection, persistent dermatitis or a reaction exceeding ordinary cosmetic tolerance.

The cancer evidence does not justify telling a client that cosmetic growth factors cause malignancy. It also does not justify declaring long-term cosmetic use proven safe. Where the client has a relevant cancer history or an unresolved lesion, the question belongs with the appropriate medical clinician.

Microneedling with a growth-factor preparation falls under the procedure pathway rather than ordinary topical skincare.[14] Practitioner competence, insurance, the authorised product route, current manufacturer instructions and appropriately governed training determine delivery.

Mechanism of action#

Growth factors bind cell-surface receptors and initiate signalling pathways that can alter proliferation, migration, differentiation and matrix synthesis. PDGF, VEGF, EGF and KGF are among factors reported to influence collagen biosynthesis.[3, 15]

For a topical cosmetic, the unresolved step is delivery. A conventional protein is much larger than the molecules that usually cross intact stratum corneum, and protein stability in emulsions is difficult.[2, 3, 4] No study was located demonstrating receptor-relevant intact growth factor from a marketed cosmetic in viable living human skin after surface application.

Modest clinical improvement and the delivery gap can both be true. Possible explanations include vehicle effects, other ingredients, follicular delivery, fragments, surface signalling or repeated moisturisation; none has been shown to account for the result.

Commonly misstated claims#

“Growth factors are too large to penetrate, so they do nothing.”

The 500 Dalton rule is a useful prior rather than a measured law, and it addresses intact stratum corneum. Controlled and uncontrolled studies report modest appearance changes, while direct intact-protein delivery has not been demonstrated.[1, 2, 5]

Supported statement: specific formulations have produced modest clinical changes, and the mechanism by which a mature growth factor contributes remains unresolved.

“Growth-factor skincare is known to cause cancer.”

The concern arose from becaplermin on open diabetic ulcers. The early mortality signal did not persist in longer follow-up, but no long-term cosmetic-user cohort exists.[9, 10]

Supported statement: medical wound-care data are broadly reassuring for recombinant PDGF-BB; long-term cosmetic exposure has not been studied.

“Plant-derived growth factors are a natural alternative to human growth factors.”

The leading barley product is recombinant human-like EGF expressed in barley, not a plant-native human growth factor.[8, 3]

Supported statement: recombinant human-sequence EGF can be produced in a plant host; its clinical evidence remains product-specific and uncontrolled.

“A 37% collagen increase proves dermal rebuilding.”

The 37% figure was Grenz-zone thickness in an uncontrolled 14-person before-and-after pilot, without a vehicle arm, randomisation or blinding.[6]

Supported statement: one small pilot reported a 37% increase in Grenz-zone thickness and 27% epidermal thickening over 60 days; causation and class-wide transfer are unestablished.

Areas of remaining uncertainty#

  • No marketed topical has demonstrated intact, bioactive growth factor at a receptor-relevant dose in viable living human skin; selection therefore rests on finished-product clinical evidence rather than penetration claims.
  • No trial isolates the growth factor from all other formulation ingredients; visible improvement cannot be assigned confidently to the labelled protein.[1, 5, 7]
  • Persistence beyond six months is unknown; short-term improvement should not be converted into a durable-remodelling claim.[1]
  • The becaplermin reassurance may transfer favourably or unfavourably to cosmetics because molecule count, dose, route and population differ; relevant cancer history remains a referral question.[9, 10]
  • Independent shelf-life data showing intact bioactive protein at the point of use were not located; the INCI alone cannot establish delivered dose.[4]
  • No UK enforcement document explains how OPSS applies Annex II entry 416 to named conditioned-media ingredients; the Responsible Person’s documented compliance position is therefore essential.[13]
  • No controlled study establishes that microneedling plus growth factors outperforms microneedling alone or defines its safety; the product and procedure instructions remain the operative boundary.[14]

Frequently asked questions#

Are topical growth factors proven to work?

Specific products have produced modest short-term improvements, but nearly three quarters of studies were uncontrolled and formulation heterogeneity prevents a class-wide promise.[1]

Can a human-derived growth-factor serum be used in Great Britain?

Annex II entry 416 prohibits cells, tissues or products of human origin in cosmetics. A human-derived INCI therefore requires a documented compliance explanation from the Responsible Person before use or retail.[13]

Are growth factors the same as exosomes?

No. Growth factors are soluble signalling proteins; exosomes are lipid-bilayer extracellular vesicles. Evidence and regulatory questions must be assessed separately.

Do growth-factor products cause cancer?

That has not been shown. Longer becaplermin follow-up was reassuring, but it studied a medicine on open ulcers and no long-term cosmetic-user epidemiology exists.[9, 10]

Can they be applied after microneedling?

Only where the exact product is intended for that route and the procedure instructions support it. Surface-cosmetic evidence does not establish safety or benefit after barrier breach.[14]

References#

Each source is graded by evidence tier. Tier 4 material (manufacturer documents, expert consensus, practitioner experience) is useful for protocol and context, and is never presented as equivalent to independent clinical evidence.

  1. Quinlan DJ, Ghanem AM, Hassan H. Topical growth factor preparations for facial skin rejuvenation: A systematic review. Journal of Cosmetic Dermatology. 2023;22(7):2023-2039. doi:10.1111/jocd.15644. PMID 37222303.Tier 1Supports: The anchor independent evidence synthesis. Authors are at Academic Plastic Surgery, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London — no manufacturer affiliation stated in the record. Searched Cochrane Library, EMBASE, MEDLINE and Scopus from 2000 to October 2022 for prospective trials and case series of 10+ participants. Included 33 studies: '9 randomized controlled trials (RCTs) and 24 uncontrolled case series, representing 1180 participants receiving 23 different topical preparations containing GFs'. Only 9 of the 33 used a placebo or active control. Preparations were applied twice daily in all but two studies; mean treatment duration 3 months. Verbatim result: 'Based on the investigator's assessment, preparations containing GFs induce a modest improvement in skin texture (median < 50%), fine lines/wrinkles (median < 35%), and overall facial appearance (median < 20%) versus baseline. Participant-assessed improvement was generally higher than investigator-assessed response. Three comparative RCTs showed no statistically significant differences between treatments.' Stated limitations, verbatim: 'Studies were limited by heterogeneity with regard to the source and number of GFs used in the preparations, information about additional ingredients, and lack of standardization in the outcome measures.' Also: 'The preparations were associated with a low risk of adverse events. The persistence of the clinical improvements beyond 6 months is not known.' SCOPE LIMITS: facial rejuvenation only; no meta-analysis of pooled effect estimates reported in the abstract; no formal risk-of-bias grading reported in the abstract; 73% of included studies were uncontrolled; funding and COI statements for the review itself could not be retrieved (Wiley full text returned HTTP 402 and Europe PMC did not display them), so I do not assert them.Funding / interest: Not verified — full text paywalled; funding and COI statements not retrievable. Author affiliation is academic (Queen Mary University of London) with no manufacturer affiliation in the PubMed record.
  2. Bos JD, Meinardi MM. The 500 Dalton rule for the skin penetration of chemical compounds and drugs. Experimental Dermatology. 2000 Jun;9(3):165-9. doi:10.1034/j.1600-0625.2000.009003165.x. PMID: 10839713.Tier 3Supports: The canonical source for the penetration ceiling. Department of Dermatology, Academic Medical Center, University of Amsterdam. Verbatim: 'We argue that the molecular weight (MW) of a compound must be under 500 Dalton to allow skin absorption. Larger molecules cannot pass the corneal layer.' Three stated arguments, verbatim: '1) virtually all common contact allergens are under 500 Dalton, larger molecules are not known as contact sensitizers. They cannot penetrate and thus cannot act as allergens in man; 2) the most commonly used pharmacological agents applied in topical dermatotherapy are all under 500 Dalton; 3) all known topical drugs used in transdermal drug-delivery systems are under 500 Dalton.' SCOPE LIMITS: this is an argument paper, not an experiment — it presents NO new penetration data and generates the rule inductively from existing pharmacological and contact-allergy literature. It concerns intact skin and does not address follicular delivery, damaged/microneedled skin, or penetration enhancers. It is 26 years old and the '500 Da' figure is a rule of thumb, not a measured hard cut-off. Do not present it as a systematic review or as a law of physics.
  3. Aldag C, Nogueira Teixeira D, Leventhal PS. Skin rejuvenation using cosmetic products containing growth factors, cytokines, and matrikines: a review of the literature. Clinical, Cosmetic and Investigational Dermatology. 2016;9:411-419. doi:10.2147/CCID.S116158. PMID 27877059; PMCID PMC5108505.Tier 4Supports: Narrative (non-systematic) review; open access full text read. Supplies the explicit size argument, verbatim: 'Molecules larger than 500 Da generally cannot easily penetrate the stratum corneum to reach the viable keratinocytes in the stratum basale', and states growth factors have a 'large molecular size (generally >15,000 Da)' which 'limits their ability to penetrate the tightly packed stratum corneum'. Gives the smallest common exception verbatim: 'EGF is a 6 kDa polypeptide growth factor'. On sourcing, it identifies TNS products as derived from 'neonatal foreskin fibroblast culture', ReGenica from hypoxically-cultured fibroblasts, PSP products as 'a mixture of growth factors and cytokines obtained as the lysate of cultured human fibroblasts', and an EGF serum using 'recombinant EGF produced in barley'. On study quality, verbatim: 'As is common in placebo-controlled dermatologic studies, the vehicle (cream base) formulated the product was used as the control', and concludes 'data are limited. These products need to be further evaluated in well-designed, randomized trials.' SCOPE LIMITS: this review is written to argue the case for matrikines over growth factors on penetration grounds — that is the sponsor's commercial interest, so the size argument is made by an interested party even though it is factually consistent with Bos & Meinardi. It discusses no plant-own, colostrum or snail-derived products. It raises NO oncological safety concern; the only tumour reference is an incidental note that 'like many growth factors, some matrikines can promote tumorigenesis, while others inhibit it'.Funding / interest: Substantial commercial interest, disclosed verbatim in the paper: 'CA and DNT are employees of Merz Pharmaceuticals GmbH, which sells products mentioned in this review. PSL is an employee of 4Clinics, which was paid for medical writing by Merz Pharmaceuticals GmbH.'
  4. Eskens O, Amin S. Challenges and effective routes for formulating and delivery of epidermal growth factors in skin care. International Journal of Cosmetic Science. 2021 Apr;43(2):123-130. doi:10.1111/ics.12685. Epub 2021 Jan 15. PMID: 33354795.Tier 4Supports: Formulation-science narrative review from Chemical Engineering Department, Manhattan College, Riverdale, NY — a non-dermatology, non-manufacturer perspective. States the formulation problem verbatim: 'Incorporation of these biologics into skincare formulations has been greatly hindered by low transdermal delivery efficacy, intricate material interactions and protein instability — especially within common cosmetic emulsions.' Also verbatim: 'Current understandings of growth factor formulating techniques in cosmetic products is limited, and the performance of other protein structures is an adequate point of reference.' The review's whole second section is devoted to 'emerging drug delivery systems to overcome the challenges of topical growth factor treatment' — i.e. it treats delivery as an unsolved problem requiring engineered vehicles, not something a conventional serum achieves. SCOPE LIMITS: narrative review, EGF-focused, no new experimental data, no quantified penetration figures in the abstract, and it is optimistic in tone about the category ('have shown promising results in skincare treatments'). It does not claim conventional cosmetic formulations fail to work clinically — only that delivery efficacy is low and protein stability is poor.
  5. Mehta RC, Smith SR, Grove GL, Ford RO, Canfield W, Donofrio LM, Flynn TC, Leyden JJ. Reduction in facial photodamage by a topical growth factor product. Journal of Drugs in Dermatology. 2008 Sep;7(9):864-71. PMID: 19112801.Tier 2Supports: The best-designed vehicle-controlled trial of a human fibroblast conditioned media product I could verify. Design: double-blind, 60 subjects randomly assigned to active gel or vehicle, applied twice daily for 6 months alongside a moisturising cleanser and sunscreen; assessments at 0, 3 and 6 months by profilometry, photography and clinical assessment. Product described verbatim as 'a topical gel containing a proprietary mixture of over 110 growth factors, cytokines, and soluble matrix proteins secreted by human dermal fibroblasts'. CRITICAL NUANCE — the result is weaker than it is usually quoted as being. Verbatim: 'Treatment with the active gel for 3 months produced greater reduction in fine lines and wrinkles than the vehicle treatment as measured by objective and subjective assessment techniques. The results were either statistically significant (P < or = .05) or trending towards statistical significance (P < or = .1).' That is, some of the reported endpoints did NOT reach conventional significance and are reported at a relaxed P ≤ 0.1 threshold. SCOPE LIMITS: n=60 total, so roughly 30 per arm; no effect sizes, confidence intervals or per-endpoint breakdown given in the abstract; the 6-month timepoint result is not separately stated; both arms also received cleanser and sunscreen, which alone improve photodamage.Funding / interest: Manufacturer study. First and corresponding author Rahul C Mehta is affiliated to SkinMedica Inc, Carlsbad, CA (rmehta@skinmedica.com) — SkinMedica markets the human fibroblast conditioned media product line. Several co-authors are well-known cosmetic dermatology investigators; individual COI not stated in the PubMed record.
  6. Fitzpatrick RE, Rostan EF. Reversal of photodamage with topical growth factors: a pilot study. Journal of Cosmetic and Laser Therapy. 2003 Apr;5(1):25-34. doi:10.1080/14764170310000817. PMID: 12745596.Tier 3Supports: The foundational and most-cited histological study for the category — and it is an UNCONTROLLED pilot, which is routinely omitted when it is cited. Design: 14 patients applied a gel containing a mixture of eight different growth factors (Nouricel-MD) to photodamaged facial skin twice daily for 60 days. Assessments: Fitzpatrick photodamage scale, 3 mm punch biopsies, optical profilometry, patient questionnaire. Verbatim results: 'Eleven of 14 patients showed clinical improvement in at least one facial area. The peri-orbital region showed a statistically significant improvement (p = 0.0003). Optical profilometry showed a statistically significant reduction in Ra measurement (p=0.0075) and shadowing (p=0.02)... Biopsies revealed new collagen formation in the Grenz zone (37% increase in thickness) and thickening of the epidermis by 27%. Eight of 14 patients felt their wrinkles were improved, while 12 of 14 felt their skin texture was improved.' The authors' own conclusion is appropriately hedged, verbatim: 'The application of a mixture of topical growth factors MAY stimulate the repair of facial photodamage' (emphasis on 'may'). SCOPE LIMITS: n=14, no control group, no vehicle arm, no randomisation, no blinding, 60 days only, single-centre, 2003. The 37% Grenz zone and 27% epidermal thickening figures are before-and-after within the same patients with nothing to compare against — they cannot attribute the change to the growth factors as opposed to the vehicle, occlusion, or twice-daily moisturisation.Funding / interest: Not stated in the PubMed record. Authors at Cosmetic Laser Associates, Scripps-XIMED Medical Center, La Jolla, CA. Nouricel-MD is the proprietary human fibroblast conditioned media base subsequently commercialised as TNS; Richard Fitzpatrick was closely associated with the company that developed it, so treat this as an interested-party study.
  7. Wu DC, Goldman MP. A Prospective, Randomized, Double-blind, Split-face Clinical Trial Comparing the Efficacy of Two Topical Human Growth Factors for the Rejuvenation of the Aging Face. Journal of Clinical and Aesthetic Dermatology. 2017;10(5):31-35. PMID 28670356; PMCID PMC5479475.Tier 2Supports: An IRB-approved randomised, double-blind, split-face trial in 20 healthy subjects with moderate-to-severe facial wrinkling secondary to photodamage; one hemiface received topical human fibroblast-derived growth factors, the other human adipose-derived mesenchymal stem cell growth factors, for three months, with blinded evaluation. Verbatim result: 'Both growth factor formulations achieved significant improvement in facial wrinkling. Blinded investigator and subject evaluations did not detect any significant differences between the two formulations in terms of efficacy, safety, or tolerability.' CRITICAL SCOPE LIMIT: there is NO vehicle or no-treatment arm. Every square centimetre of every face received an active product, so the trial cannot show that either preparation outperformed a plain moisturiser, and the 'significant improvement in facial wrinkling' is a within-subject before-and-after finding, not a placebo-controlled one. n=20, three months, single centre. This is a head-to-head equivalence result, not evidence of efficacy against vehicle. It is one of the three comparative RCTs whose null between-arm result feeds Quinlan's finding.Funding / interest: Manufacturer-funded with a disclosed consultancy. Verbatim: 'Dr. Wu reports no relevant conflicts of interest. Dr. Goldman is a consultant for Nuderm and SkinMedica. The study was funded by Nuderm.' Both compared products are from companies to which the senior author consults or which funded the study.
  8. Schouest JM, Luu TK, Moy RL. Improved texture and appearance of human facial skin after daily topical application of barley produced, synthetic, human-like epidermal growth factor (EGF) serum. Journal of Drugs in Dermatology. 2012;11(5):613-620. PMID 22527430.Tier 3Supports: The reference study for bioengineered, plant-expressed recombinant EGF — the route used to avoid human-derived material. Verbatim design: 'A three month, open-label, single center study... Twenty-nine females, aged 39 to 75 years, with mild to severe, fine and course rhytids, photodamage, and pigmentation were enrolled. Subjects then applied the treatment serum per the prescribed protocol twice-daily for 3 months, in addition to the use of a basic sunscreen and facial cleanser.' Verbatim result: 'Clinical evaluations showed statistically significant improvement in the appearance of fine lines and rhytids, skin texture, pore size, and various dyschromatic conditions apparent within the first month of use, and continuing improvement trends for the duration of the study. The treatment serum was well tolerated with minimal treatment-related complications reported throughout.' KEY TERMINOLOGY POINT: the active is described as 'barley bioengineered, human-like epidermal growth factor protein' — barley is used as a recombinant expression host for a human-sequence protein; this is not a growth factor native to barley. SCOPE LIMITS: open-label, single-centre, uncontrolled, no randomisation, no blinding, no vehicle arm, n=29, women only, 3 months. Every subject also used sunscreen and cleanser, both of which improve photodamage measures on their own. No effect sizes or P values given in the abstract.Funding / interest: Not stated in the PubMed record. Authors at Moy-Fincher-Chipps Facial Plastics and Dermatology, Beverly Hills, CA; Ronald Moy has commercial involvement in barley-derived EGF skincare, so treat as an interested-party study.
  9. Ziyadeh N, Fife D, Walker AM, Wilkinson GS, Seeger JD. A matched cohort study of the risk of cancer in users of becaplermin. Advances in Skin & Wound Care. 2011;24(1):31-39. doi:10.1097/01.ASW.0000392922.30229.b3. PMID 21173589.Tier 3Supports: The single best real-world human dataset on a topically applied recombinant growth factor and cancer, and the origin of the whole 'growth factors and cancer' debate. Design: matched cohort in an insured population; becaplermin (recombinant human PDGF, topical) initiators matched to non-initiators, followed up to 6 years for cancer incidence and up to 9 years for cancer mortality; incidence validated by medical record review; mortality via National Death Index linkage. Verbatim numbers: 'Among 1622 becaplermin initiators, there were 28 confirmed cancers and 9 cancer deaths, and among the 2809 matched comparators, there were 43 confirmed cancers and 16 cancer deaths. There was no increased risk of cancer with becaplermin (hazard ratio, 1.2; 95% CI, 0.7-1.9). Cancer mortality through 2003 was increased (rate ratio [RR] = 5.2; 95% CI, 1.7-17.6) among subjects with 3 or more dispensings. Additional follow-up through 2006 indicated no elevated cancer mortality risk overall (RR, 1.0; 95% CI, 0.5-2.3) and no statistically significant increase in the subgroup with more than 3 dispensings (RR, 2.4; 95% CI, 0.8-7.4).' Conclusion verbatim: 'Becaplermin does not appear to increase the risk of cancer or cancer mortality.' Background context verbatim: 'Extended follow-up of patients from clinical trials of becaplermin compared with placebo identified a relative risk of cancer of 2.8 (95% confidence interval [CI], 0.6-12.8).' SCOPE LIMITS — these matter enormously for a skincare entry: becaplermin is a PRESCRIPTION MEDICINE applied to OPEN lower-extremity diabetic neuropathic ULCERS at pharmacological concentration, in an older, diabetic, comorbid population — not a cosmetic on intact facial skin. It is a single growth factor (PDGF-BB), not a conditioned-media mixture. The reassuring point estimates sit on small event counts (9 vs 16 cancer deaths) with wide confidence intervals; the residual RR of 2.4 (0.8-7.4) in the high-exposure subgroup is not significant but is not reassuring either. Observational design with confounding by indication.Funding / interest: Funding statement not shown in the PubMed record. Lead author affiliated to Ingenix / i3 Drug Safety, Waltham, MA — a contract pharmacoepidemiology organisation typically commissioned by manufacturers for post-marketing safety studies. Treat manufacturer commissioning as likely but unverified; I did not confirm it.
  10. Hee CK, Slade HB, Lynch SE. Safety of Exogenous Recombinant Human Platelet-Derived Growth Factor-BB (rhPDGF-BB) for Medical and Cosmetic Applications: A Review. Journal of Cosmetic Dermatology. 2026;25(1):e70636. doi:10.1111/jocd.70636. PMID 41472395; PMCID PMC12754275.Tier 4Supports: The most recent synthesis of the rhPDGF-BB oncological safety question, and it carries the heaviest conflict of interest in this package — read it as an interested party's brief, not a neutral appraisal. Narrative (non-systematic) review. Reports the regulatory arc: a 2008 boxed warning was added to REGRANEX applying only to use of three or more tubes, and was later removed. Reports four epidemiological datasets, verbatim where quoted: (i) the initial matched cohort of 1,622 REGRANEX patients vs 2,809 unexposed with up to 3 years follow-up identified 'a potential risk for increased mortality when dispensed 3 or more tubes'; (ii) 'Longer term follow-up (up to 6 years) of the high dose REGRANEX cohort showed no increased risk of cancer incidence or mortality'; (iii) the largest study, a Veterans Administration cohort of 6,429 REGRANEX users vs 6,429 matched comparators over 11 years — 'The hazard ratio for cancer mortality among those who received 3 or more tubes of REGRANEX Gel relative to those who received none was 1.04 (95% confidence interval 0.73–1.48)'; (iv) in a prior-cancer cohort, '87 cancer deaths in the REGRANEX-exposed cohort (n = 477) and 340 cancer deaths in the matched comparator cohort... resulting in a hazard ratio of 0.9 (95% CI, 0.7–1.2)'. SCOPE LIMITS: narrative review by authors with a direct commercial stake in rhPDGF-BB; covers ONE growth factor (PDGF-BB) in wound-care and injectable/implant settings, not multi-growth-factor cosmetic serums on intact skin; no systematic search methodology or risk-of-bias assessment; the underlying VA data are observational.Funding / interest: Major undisclosed-by-default commercial stake, disclosed verbatim in the paper: 'C.K.H. and S.E.L. are employees of and own stock and/or options in Lynch Regenerative Medicine LLC. H.B.S. is a consultant of Lynch Regenerative Medicine LLC.' Samuel E Lynch is the founder of the company whose core technology is rhPDGF-BB. Affiliations: Lynch Regenerative Medicine, Franklin, Tennessee (Hee, Lynch); Chisholm Clinical Research Services LLC, Ft. Worth, Texas (Slade). No external funding source stated.
  11. Fabi SG, Cohen JL, Peterson JD, Kiripolsky MG, Goldman MP. The Effects of Filtrate of the Secretion of the Cryptomphalus aspersa on Photoaged Skin. Journal of Drugs in Dermatology. 2013;12(4):453-457. PMID 23652894.Tier 2Supports: The primary placebo-controlled evidence for snail secretion filtrate, which is routinely marketed under the growth factor banner. Verbatim design: 'a 2-center, double-blind, randomized, 14-week study in which 25 patients with moderate to severe facial photodamage were treated with an emulsion (with 8% SCA) and liquid serum (with 40% SCA) on one side of the face and placebo on the contralateral side for 12 weeks.' Objective measure: silicone skin impressions of periocular rhytides at baseline and 12 weeks, plus patient and physician assessments at 8, 12 and 14 weeks. POSITIVE FINDING, verbatim: 'Periocular rhytides on the active ingredient side showed significant improvement after 12 weeks (P=.03) and improved texture to a greater degree than placebo at 8 and 12 weeks, as well as 2 weeks after discontinuing the product (14 weeks).' Also verbatim, and less flattering: 'Subjects noted a significant degree of improvement in fines lines at the 8-week time point on the SCA-treated side (P≤.05) but did not report a significant difference in the quality of their skin.' TERMINOLOGY SCOPE LIMIT: the paper's own framing is that 'GFs may be derived from a variety of sources, including animals' — but SCA is a snail secretion, and neither this paper nor the product claims it contains human EGF, TGF-beta, VEGF, KGF or PDGF. n=25, 12 weeks of treatment, single ingredient system, no histology, split-face design vulnerable to product migration across the midline.Funding / interest: Not stated in the PubMed record. Authors at Cosmetic Laser Dermatology, San Diego, CA — a practice with extensive industry relationships; individual disclosures not shown in the record.
  12. Lim VZ, Yong AA, Tan WPM, Zhao X, Vitale M, Goh CL. Efficacy and Safety of a New Cosmeceutical Regimen Based on the Combination of Snail Secretion Filtrate and Snail Egg Extract to Improve Signs of Skin Aging. Journal of Clinical and Aesthetic Dermatology. 2020;13(3):31-36. PMID 32308795; PMCID PMC7159309.Tier 2Supports: A vehicle-controlled RCT of snail-derived actives, and the source of the single most useful honest negative in the snail literature. Verbatim design: 'A three-month, single-center, double-blinded, randomized, vehicle-controlled trial... Fifty women, aged 45-65 years, with signs of photoaging were randomized to receive either the active ingredients (n=30) or vehicle (n=20).' Critically, the paper describes SCA as having 'fibroblast growth factor-LIKE activity' (emphasis added) and IFC-CAF snail egg extract as having 'skin stem cell activation activity' — i.e. the claim is bioactivity resembling a growth factor, not the presence of human growth factors. Verbatim results: 'Subjects in the active treatment group experienced reductions in transepidermal water loss and significant improvements in skin roughness, firmness, and elasticity. BOTH GROUPS SHOWED SIGNIFICANT IMPROVEMENTS IN FINE LINES AND WRINKLES. PGA and IGA assessments indicated greater improvement in the active treatment group.' The vehicle alone significantly improved fine lines and wrinkles — the headline consumer endpoint did not separate active from vehicle. Authors' own conclusion verbatim: 'Larger randomized, controlled studies are needed to confirm our results.' SCOPE LIMITS: n=50 unequally randomised 30:20, single centre (National Skin Centre, Singapore), women aged 45-65 only, 3 months, no effect sizes or confidence intervals in the abstract, combination regimen so individual ingredient contributions cannot be separated.Funding / interest: Manufacturer-funded with an employee co-author, disclosed verbatim: 'FUNDING: This work was supported by grants from Cantabria Labs. DISCLOSURES: Dr. Goh is an advisory board member for Cantabria Labs. Dr. Vitale is an employee of Cantabria Labs. The other authors have no conflicts of interest relevant to the content of this article.'
  13. Regulation (EC) No 1223/2009 on cosmetic products, Annex II, reference number 416, as assimilated law applying in Great Britain. legislation.gov.uk. Accessed 1 August 2026.Tier 1Supports: Primary UK legal source, fetched and read directly on legislation.gov.uk. The Annex is titled verbatim 'ANNEX II U.K. LIST OF SUBSTANCES PROHIBITED IN COSMETIC PRODUCTS'. Reference number 416 in the substance identification column reads verbatim: 'Cells, tissues or products of human origin'. The page carries the UK editorial note that this is EU-origin legislation maintained on legislation.gov.uk and updated with any amendments made by the UK since IP completion day (31 December 2020). SCOPE: this is a prohibition on the substance being present in a cosmetic product placed on the GB market. It is in force now — it is not a proposal and not consultation material. LIMITS: the legislation text itself does not name specific commercial ingredients, so the application of entry 416 to any named product (e.g. an INCI-listed 'human fibroblast conditioned media') is an interpretive step, not a quotation from the legislation. Northern Ireland follows the EU Cosmetics Regulation under the Windsor Framework; the substance of entry 416 is the same in both.
  14. Joint Council for Cosmetic Practitioners. The Procedures that are Regulated by the JCCP — Introduction to non-surgical aesthetic treatments and hair restoration surgery. JCCP website. Accessed 1 August 2026.Tier 4Supports: Fetched and read directly. The JCCP lists five procedural modalities it registers against prescribed practice standards, verbatim: 'Botulinum Toxins'; 'Dermal Fillers'; 'Skin Rejuvenation – Micro Needling and Peels'; 'Lasers and Light (LIPLED)'; 'Hair Restoration Surgery'. The page describes these as 'the treatments that we regulate currently according to a set of prescribed practice standards' and notes the list 'are likely to increase in number in the future as new risks to person/patients are identified'. SCOPE LIMITS: the JCCP is a voluntary register and the CPSA sets voluntary standards — neither is a statutory regulator, and neither list has the force of law. Topical application of a cosmetic product is not itself one of the five modalities; the relevance here is that delivering a growth factor product via microneedling brings the procedure into the 'Skin Rejuvenation – Micro Needling and Peels' modality.
  15. UniProt Consortium. UniProtKB reviewed human protein records: EGF (P01133), TGF-beta-1 (P01137), VEGF-A (P15692), FGF7/KGF (P21781), and PDGF-B (P01127). Accessed 1 August 2026.Tier 4Supports: Curated protein sequence database — used only for the physical size of the five growth factors named in the brief, all fetched individually and read. EGF (P01133, EGF_HUMAN): mature EGF is the CHAIN at residues 971–1023, i.e. 53 amino acids, excised from a 1,207-residue, 133,994 Da pro-EGF precursor. TGF-beta-1 (P01137, TGFB1_HUMAN): mature chain residues 279–390, i.e. 112 amino acids, and the active form is a 'Homodimer; disulfide-linked'; precursor 390 residues / 44,325 Da. VEGF-A (P15692, VEGFA_HUMAN): mature chain residues 207–395, i.e. 189 amino acids, active as a 'Homodimer; disulfide-linked'; precursor 395 residues / 43,597 Da. KGF/FGF7 (P21781, FGF7_HUMAN): mature chain residues 32–194, i.e. 163 amino acids after cleavage of a 31-residue signal peptide; precursor 194 residues / 22,509 Da. PDGF-B (P01127, PDGFB_HUMAN): mature chain residues 82–190, i.e. 109 amino acids, forming an antiparallel disulfide-linked homodimer (PDGF-BB) or a heterodimer with PDGF-A; precursor 241 residues / 27,283 Da. SCOPE LIMITS: the molecular weights quoted in the SQ lines are for the PRECURSOR proteins, not the mature chains — I have therefore reported mature forms in amino-acid counts rather than asserting unsourced kDa figures. UniProt is a sequence database, not clinical evidence, and says nothing about skin penetration, formulation stability or efficacy.