What the Evidence Says: A Dermatologist's Scorecard of Popular Skin and Hair Claims
Short answer: This page collects the skin and hair claims patients ask me about most and grades each one by the strength of the scientific evidence: Strong, Moderate, Limited or Insufficient. Every entry links to the article where I examine the claim in detail. In brief: retinoids and oral JAK inhibitors for severe alopecia areata have strong evidence; PRP and low-dose oral minoxidil for pattern hair loss are moderate; collagen supplements, salmon DNA and skin cycling are limited; exosomes, gua sha and biotin in people without a deficiency are insufficient for what they promise.
Every week social media produces a new “miracle” for skin or hair. Instead of starting from scratch in every consultation, I keep this scorecard: one line per claim, its evidence level and a link to the full article. It is the index of the “What the Evidence Says” series and is updated as new articles are added. The three-line box at the top of each article (claim, evidence level, my recommendation) is the short version of the same assessment.
How I grade the evidence
Not all evidence carries the same weight. I use this order:
Strong: a current guideline recommendation, a systematic review or several well-designed randomised controlled trials point in the same direction.
Moderate: positive randomised trials exist, but they are few, protocols are not standardised or long-term data are missing.
Limited: small, short studies, often with weak control groups or industry funding; there is a signal but no firm conclusion.
Insufficient: no meaningful human evidence for the promised result; only laboratory or animal data, a plausible mechanism or isolated observations.
Two things do not count as evidence: advertising and single cases. A before-and-after photo, a celebrity endorsement or “it worked for me” can be a hypothesis, not proof. An effect seen in cells in the laboratory does not guarantee the same result in people.
The grade applies to a specific claim, not to the method as a whole. “Insufficient” means the promised result is not supported, not that the method does nothing at all. These four levels are a simplified, patient-friendly summary based on the GRADE approach and the evidence pyramid used in evidence-based medicine; they are not a formal GRADE assessment.
Strong evidence
Retinoids genuinely improve acne and signs of skin ageing — Strong — Among the most thoroughly studied topical treatments; tretinoin is the strongest and needs medical supervision, while retinol is gentler and slower. → Tretinoin vs retinol
Oral JAK inhibitors can regrow hair in severe alopecia areata — Strong — In placebo-controlled phase 3 trials roughly a quarter to two-fifths of patients regained hair on at least 80% of the scalp; the effect lasts only while the medicine is taken and requires blood tests and medical follow-up. → JAK inhibitors for alopecia areata
Moderate evidence
PRP strengthens hair in pattern hair loss — Moderate — Randomised trials support it in early androgenetic alopecia as an add-on to medical treatment, but protocols vary and it does not revive follicles that are already gone. → Hair PRP: what the evidence says
Low-dose oral minoxidil works for pattern hair loss — Moderate — In randomised trials its effect was close to topical minoxidil, without a clear advantage; it is used off-label and needs medical assessment with blood pressure and pulse monitoring. → Low-dose oral minoxidil
Limited evidence
Collagen supplements erase wrinkles — Limited — Some randomised trials show small gains in hydration and elasticity, but studies are short, small and often industry-funded; wrinkle-erasing has no evidence. → Collagen supplements
Salmon DNA (polynucleotide) injections improve skin quality — Limited — Studies report better elasticity and hydration, but most are small and short and comparisons with established treatments are limited. → Salmon DNA: hype or science?
Skin cycling is a smarter skincare routine — Limited — A sound way to rotate active nights and recovery nights, but it is repackaged irritation management rather than a separately proven method. → Skin cycling
Insufficient evidence
Exosome treatments regenerate skin and stop hair loss — Insufficient — Human studies are small and short, products differ widely, and none is approved for dermatologic or aesthetic use. → Exosome treatments
Gua sha and face yoga lift sagging skin — Insufficient — Massage can ease morning puffiness for a few hours; it cannot reach the deep structures behind sagging. → Gua sha and face tools
Biotin stops hair loss — Insufficient — Benefit has been shown only in biotin deficiency, which is rare, and high doses can distort some blood tests. → Biotin and hair loss
Mineral sunscreen is superior because it is “natural” — Insufficient — Both filter types are approved and effective; what matters is applying enough every day. → Mineral vs chemical sunscreen
Facial hollowing after weight loss on GLP-1 medication is permanent — Insufficient — It is loss of facial fat pads, not permanent damage, and it responds to volume restoration and tightening once weight is stable. → Facial sagging after rapid weight loss
All articles in the series: What the Evidence Says category
Frequently asked questions
Does an “Insufficient” grade mean a method is useless?
No. It means there are not enough human studies supporting the promised result. Some methods may still help a little with something else; gua sha, for example, can ease morning puffiness for a few hours. The grade applies to the result being advertised.
Why don't adverts and before-and-after photos count as evidence?
Lighting, angle, filters, other treatments done at the same time and natural improvement all change the result, and there is no comparison group. Only controlled, ideally randomised, studies can show what a method really does.
Can the grades change?
Yes. Grades are updated as new randomised trials and guidelines are published; every article shows the date it was last updated.
Is this scorecard a treatment recommendation for me?
No. The evidence level shows how well a method is supported in general. Whether it suits you depends on your diagnosis, skin type and health, and is decided at examination.
References
Guyatt GH, Oxman AD, Vist GE, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ. 2008;336(7650):924-926. DOI
Murad MH, Asi N, Alsawas M, Alahdab F. New evidence pyramid. Evid Based Med. 2016;21(4):125-127. DOI
OCEBM Levels of Evidence Working Group. The Oxford Levels of Evidence 2. Oxford Centre for Evidence-Based Medicine. CEBM
This article is for general information; diagnosis and treatment are decided after examination.
Last updated: 24 October 2026 · Dr. Kağan Cingöz, MD, dermatologist
Contact
WhatsApp: +90 555 209 09 39 · info@drkagancingoz.com · İstasyon Mahallesi, Edirne Caddesi No:102, Kırklareli, Türkiye
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