Interesting new Skin Care Science, Innovations and Practices

#1

Thought I’d create this new thread on new skin care science and innovations. Post about any new developments, or good science, on skin care. Not from vendors - but from independent sources - like dermatologists and scientists.

E.g.:

CGPT5.1 Evaluation:

Polynucleotide (PN/PDRN) injections and “salmon sperm facials” are related but not equivalent interventions:

  • Injections: there is a biologically plausible mechanism and a small–moderate but growing body of human data for wound healing, scar outcomes, and modest photoaging improvements.
  • Facials/topicals: evidence is much weaker; most claims are extrapolated from injection data and small cosmetic studies, plus marketing.

Below is a structured pass through mechanism, clinical evidence, and what’s actually known vs hype.

1. What are we talking about?

Polynucleotides / PDRN

  • “PN” or “PDRN” (polydeoxyribonucleotide) are fragments of DNA (typically 50–1500 kDa) purified from salmon or trout sperm (Oncorhynchus species).([PMC][1])
  • They act mainly via adenosine A2A receptor activation → ↑cAMP → ↑VEGF/angiogenesis, fibroblast proliferation, collagen synthesis, and anti-inflammatory signalling.([MDPI][2])
  • In some jurisdictions, PDRN is a licensed drug for chronic wounds and tissue repair; the cosmetic “skin booster” use is mostly off-label or regulated as devices/fillers.([PMC][1])

“Salmon sperm” branding

  • The “salmon sperm” phrase is largely marketing; clinically, you’re getting purified, sterilized DNA fragments, not whole cells.([PMC][1])

Regulatory context (important)

  • In the US, PDRN is only approved in topical forms (post-procedure, wound-healing style uses). Injectable PN/PDRN “skin boosters” are not FDA-approved; use is off-label or via imported products with uncertain oversight.([Allure][3])
  • Korea, parts of Europe, and some Asia-Pacific markets have approved PN/PDRN products for wound healing and as dermal fillers/skin boosters.([MDPI][4])

2. Mechanistic plausibility for skin benefits

Preclinical and mechanistic work is reasonably consistent:

  • PDRN/PN stimulate fibroblast proliferation and collagen I/III synthesis, improve dermal matrix organization, and increase dermal thickness in vitro and in animals.([ScienceDirect][5])
  • They enhance angiogenesis and re-epithelialization via VEGF upregulation, improving granulation tissue and wound closure.([MDPI][2])
  • They show anti-inflammatory effects (↓TNF-α, IL-1β, IL-6, iNOS) in skin injury models.([Juniper Publishers][6])

Mechanistically, using PN/PDRN as a regenerative adjunct for injured or photodamaged skin is plausible. The question is: how strong is human outcome data, especially for aesthetic indications?

3. Clinical evidence for injected polynucleotides

3.1 Wound healing and scars (medical indications)

This is where evidence is strongest:

  • Pressure ulcers & diabetic wounds – multiple RCTs show faster wound closure and greater reduction in ulcer area with injectable PDRN vs placebo.([JKMS][7])
  • Skin graft donor sites – randomized double-blind trial: PDRN-treated donor sites showed significantly larger re-epithelialized area at day 10 and more complete re-epithelialization by day 14 vs placebo.([ResearchGate][8])
  • Post-surgical scars – PNs injected around thyroidectomy or other surgical scars reduced scar width and improved validated scar scores vs saline at 6 months.([MDPI][9])

Takeaway: For wound healing and prevention/improvement of hypertrophic scars, injected PN/PDRN has decent RCT support with clinically meaningful effect sizes. This underpins the “regenerative” narrative.

3.2 Wrinkles, texture, and general “rejuvenation”

Here the signal is real but more modest and heterogeneous.

Key sources:

  1. Systematic/narrative reviews (2022–2025)

    • Multiple reviews conclude that PNs/PDRN can improve skin elasticity, hydration, and fine wrinkles, but emphasize that most studies are small, often uncontrolled or split-face, and methodologically variable.([MDPI][2])

  2. Rejuran and PN fillers vs comparators

    • A widely cited phase III RCT comparing PN filler (Rejuran®) to HA filler for crow’s feet (split-face, 72 patients) suggested similar wrinkle correction with somewhat longer durability for PN.([PubMed][10])
    • However, this article was later retracted by the journal, which materially weakens the evidence base for Rejuran’s superiority over HA for wrinkles.([PubMed][10])
    • Later reviews still describe PN as a “biostimulatory filler” with perceived good durability, but acknowledge reliance on limited or lower-level evidence.([PMC][11])

  3. Skin boosters / mesotherapy-style PN injections

    • Small RCTs and split-face studies report

      • ~15% improvement in skin hydration and ~20% in elasticity vs baseline or control at 8–12 weeks.([mineclinic.com][12])
      • Improvement in lateral canthal lines comparable to other biostimulatory fillers (e.g., polycaprolactone), sometimes with quicker onset and fewer local reactions.([PMC][11])

    • Case series and uncontrolled cohorts report improved texture, pore size, and subjective “glow,” but these are Level III–IV evidence at best.([MDPI][2])

  4. Acne scars and other dermatoses

    • A randomized controlled trial of intra-lesional PDRN for acne scars showed greater scar score reduction vs control (often PRP or saline), but patient numbers were small and follow-up short.([Sunset Medspa][13])

Net assessment for injections:

  • Evidence quality: mixed – from Level I/II RCTs in wound healing down to small, often industry-linked or uncontrolled aesthetic studies.
  • Effect size (photoaging): appears modest, comparable to other injectable biostimulators; not a replacement for HA fillers or long-term tretinoin, but plausible as an adjunct.
  • Big caveat: the most frequently quoted “crow’s feet” RCT in support of Rejuran’s wrinkle efficacy is retracted, and much of the rest is low-to-moderate quality and concentrated in East Asian populations. Generalizability and durability beyond 6–12 months are unclear.

Full analysis:

#2

More general, but science-based:

Stop Guessing Your Skincare Routine. A Dermatologist Breaks It All Down

ChatGPT5.1 Summary:

A. Executive Summary (150–300 words)

The video is a dermatology-focused Q&A addressing practical formulation differences, ingredient performance, and routine design. Core emphasis: most consumer confusion stems from misunderstanding mechanisms—urea vs hydroxyethyl urea, azelaic acid strengths, retinoid usage patterns, exfoliant-induced dehydration, and LED vs microneedling efficacy. The creator repeatedly clarifies that many perceived “wrinkles” from AHA overuse are dehydration lines rather than structural dermal changes, and these resolve with cessation and moisturization.

She reaffirms that urea is both a humectant and a keratolytic (≥10%), whereas hydroxyethyl urea is strictly hydrating. She stresses that azelaic acid 10% cosmetics lack the proven therapeutic impact of 15–20% prescription formulations, though they can support redness reduction. She rejects unnecessary alternation between retinoids (e.g., adapalene + tretinoin) and argues for sticking to one consistently.

LED therapy is validated for collagen stimulation, inflammation reduction, and acne management if device quality and wavelength specificity are adequate; at-home microneedling is discouraged due to infection risk and insufficient needle depth. She reiterates no meaningful need to “wait between layers” except before sunscreen, which must be applied to dry skin.

Regarding collagen biology: dietary vitamin C suffices for retinoid-mediated collagen stimulation as long as scurvy is absent. Supplementation is not evidence-based for skin benefit. Retinoids, azelaic acid, and ivermectin can be combined for rosacea management.

Video concludes with product favorites and minor personal updates; these have no scientific relevance.

B. Bullet Summary (12–20 bullets)

  • Urea ≥10% is keratolytic; hydroxyethyl urea is only hydrating.
  • Urea improves epidermal water content and texture long-term.
  • Azelaic acid can be layered with tretinoin; order does not matter.
  • Cosmetic 10% azelaic acid has weaker evidence vs 15–20% prescription formulations.
  • Overexfoliation with AHAs causes dehydration lines, not true wrinkles.
  • Lactic acid >12% can thicken epidermis/dermis but is too irritating for eyelids.
  • Using adapalene on some nights and tretinoin on others is unnecessary.
  • Retinoids are intended for nightly use once tolerated.
  • Urea 5% before tretinoin is generally tolerated and helpful for dryness.
  • Body moisturizing frequency is highly individualized; menopause increases need.
  • Some moisturizers maintain skin hydration for 48–72 hours.
  • Copper peptides can be used with azelaic acid.
  • Home LED devices work if using validated wavelengths and reputable manufacturers.
  • Cheap LED devices may overheat or aggravate melasma.
  • At-home microneedling is discouraged due to contamination and inadequate depth.
  • No need to wait between product layers except before sunscreen.
  • Adequate dietary vitamin C enables collagen synthesis; supplementation adds no benefit.
  • Tretinoin, azelaic acid, and ivermectin are compatible for rosacea management.
  • Demodex reduction likely mediates ivermectin’s benefit in rosacea.

D. Claims & Evidence Table

Claim Evidence Provided in Video Assessment
Urea ≥10% acts as a keratolytic Dermatologic mechanism: dissolves corneocyte adhesions Strong (dermatology consensus; see e.g., J Dermatolog Treat)
Hydroxyethyl urea is hydrating but not keratolytic Ingredient function and formulation practice Moderate–Strong (supported by cosmetic chemistry literature)
Cosmetic 10% azelaic acid is weaker than 15–20% Rx Notes lack of data for 10% treating acne/rosacea Strong (clinical trials support Rx, not cosmetic concentrations)
AHA overuse causes “dehydration wrinkles,” not structural wrinkles Observational dermatology experience Moderate (consistent with barrier impairment literature)
Retinoids should be used nightly once tolerated Based on clinical protocols and study design Strong
LED therapy (red/NIR) improves collagen and inflammation Mechanistic and clinical data referenced vaguely Moderate–Strong (supported in peer-reviewed trials; e.g., Dermatol Surg)
Blue light can aggravate melasma Heat and high-energy light caution Moderate (supported by some pigment biology studies)
At-home microneedling increases risk of infection Discussion of sterility concerns Strong
Vitamin C supplementation does not meaningfully enhance collagen production in skin Excess excreted; adequate levels from diet sufficient Moderate–Strong (supports dermatology consensus)
Tretinoin + azelaic acid + ivermectin combination is safe for rosacea Based on common dermatologic practice Moderate

E. Actionable Insights (5–10 items)

  1. For keratolytic smoothing (elbows, knees, rough texture), use urea ≥10%, not hydroxyethyl urea.
  2. For acne, rosacea, or hyperpigmentation, prefer 15–20% azelaic acid formulations over cosmetic 10%.
  3. If skin appears more wrinkled after AHAs, stop exfoliants and rehydrate; expect improvement.
  4. Choose one retinoid (tretinoin or adapalene) and use consistently to maximize benefit.
  5. Apply sunscreen to dry skin only to prevent pilling and ensure film formation.
  6. If using LED, buy from validated manufacturers (e.g., Omnilux) and use regularly; consistency determines results.
  7. Avoid at-home microneedling due to infection risk and inadequate needle depth.
  8. Do not use vitamin C supplements solely for collagen; maintain adequate dietary intake instead.
  9. For rosacea regimens, tretinoin + azelaic acid + ivermectin is a compatible combination when tolerated.
  10. Incorporate urea-based moisturizers during winter to reduce transepidermal water loss.

H. Technical Deep-Dive (optional analysis)

Urea vs Hydroxyethyl Urea

  • Urea enhances corneocyte hydration by disrupting hydrogen bonding within keratin and functioning as an NMF (Natural Moisturizing Factor).
  • At ≥10%, it reduces corneodesmosome integrity, yielding keratolysis.
  • Hydroxyethyl urea is non-keratolytic; used for humectancy only and lacks the biochemical interactions needed for corneocyte shedding.

Azelaic Acid Mechanism

  • Dicarboxylic acid inhibiting tyrosinase, keratinocyte hyperproliferation, and Cutibacterium acnes.
  • Prescription concentrations reach therapeutic dermal levels via percutaneous gradient; 10% cosmetics generally do not.

Retinoid Signaling

  • Tretinoin → RAR activation → ↑ collagen I/III synthesis, ↓ MMP-1.
  • Requires only physiologic intracellular vitamin C for proline/lysine hydroxylation in collagen biosynthesis.

LED Photobiomodulation

  • Red/NIR photons stimulate cytochrome c oxidase, increasing mitochondrial ATP and modulating ROS signaling → fibroblast proliferation and collagen synthesis.

Rosacea and Demodex

  • Ivermectin reduces Demodex folliculorum density and suppresses inflammatory pathways (TLR2-mediated).

I. Fact-Check of Important Claims

Claim Evidence Check Accuracy
Urea ≥10% = keratolytic Supported by dermatology literature (e.g., PubMed: PMID 31768632) Accurate
LED increases collagen Supported by RCTs showing increased procollagen and dermal density (Dermatol Surg, PMID 21091365) Accurate
Vitamin C supplements enhance skin collagen RCTs do not support enhanced cutaneous collagen from oral C in non-deficient individuals Correct to reject
Blue light aggravates melasma Some evidence shows HEVL (400–450 nm) may worsen hyperpigmentation (PMID 32758856) Plausible
Adapalene + tretinoin combo unnecessary Supported by standard-of-care protocols favoring monotherapy Accurate
At-home microneedling unsafe Consistent with dermatology warnings about sterility and needle integrity Accurate
#3

India pricing on prescription Azelaic Acid Products:

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