Salmon DNA (PDRN) Is Now Everywhere in Skincare. But Does It Actually Work?
Dermatologist and geneticist Dr. Macrene Alexiades explains why topical PDRN may not penetrate intact skin — and which skincare ingredients have stronger evidence behind them.
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Salmon DNA has become one of skincare’s buzziest ingredients.
PDRN (polydeoxyribonucleotide) started out in Korean dermatology clinics and has been showing up on serum labels, often alongside other “regenerative” ingredients like exosomes and growth factors. But can something derived from DNA actually get where it needs to go when you put it on your face?
To understand what the science says, Dr. Macrene Alexiades, a board-certified dermatologist who holds both an MD from Harvard Medical School and a PhD in genetics and who develops her own skincare formulations, breaks it down.
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The first issue, she says, is getting PDRN through the skin at all.
Your skin’s outermost layer, the stratum corneum, is built to keep things out. A widely cited paper laid out what’s known as the 500 Dalton rule. A compound generally needs to weigh less than about 500 daltons to pass through healthy skin in any meaningful amount.
PDRN is a blend of DNA fragments taken from salmon trout or chum salmon sperm. Its molecules range from 50 to 1,500 kilodaltons, and most fall between 80 and 200 kilodaltons, or 80,000 to 200,000 daltons. “Topically, these are very large molecules,” Alexiades says. “Anything above roughly 500 daltons is unable to cross an intact stratum corneum, and PDRN is orders of magnitude larger.”
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She’s clear about where a serum’s benefit stops. “What a topical PDRN can do is hydrate and support the barrier, but its other effects are observed when it is administered by injection. The science behind it is as an injectable.”
“Specifically, PDRN has a stimulatory effect on cell growth, which can be helpful in some circumstances of wound healing,” she notes of the injectable form.
Asked what’s most overhyped in skincare right now, Macrene lands on a single word: “The word ‘regenerative’ on a topical product is the most overhyped. It implies a biological result that most of these products have not demonstrated on skin.”
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Exosomes, the tiny packages cells use to send signals to each other, made a similar jump from clinics to cosmetics counters. “Exosome products have no standardized isolation, characterization, or dosing,” she explains, “so two products with the same name can be entirely different.”
Growth factors run into the same size problem as PDRN. They are, in Macrene’s words, “large, fragile proteins that are difficult to stabilize and even harder to deliver through intact skin.” The human data that exist involve delivering them through microneedling or RF microneedling, “which is a procedure, not a cream.” As she puts it, “My PhD was in stem cell biology, and I am enthusiastic about this field. But enthusiasm should follow evidence, not marketing.”
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Before Macrene would formulate with any of these ingredients, she wants to see a defined, reproducible ingredient that she can actually deliver to its target in skin from a finished product. She also wants basic science on how it works and whether it’s safe. Ideally, she’d see randomized, vehicle-controlled human trials measured with objective tools like histology and quantitative clinical outcomes, “not just consumer perception.” Anything that signals through growth pathways needs its own safety profile on top of that.
“In my Healio column on peptides, I grade evidence and flag safety concerns separately for exactly this reason,” Macrene says. “An ingredient that is biologically active deserves scrutiny in proportion to its activity.”
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Asked what’s worth the money, she says she ranks in order of strength of evidence. “Daily broad-spectrum sunscreen, topical vitamin C with vitamin E and ferulic acid, niacinamide, and hyaluronic acid for hydration.” Peptides make her list, too. “Well-studied peptides such as palmitoyl pentapeptide-4 and DNA repair ingredients have a significant place as well.”
“Those are the ingredients with human data over years, not months,” she points out. “Everything beyond that is an addition to a foundation, not a replacement for it.” She calls vitamin C with vitamin E and ferulic acid the best-known synergy in skincare, because the combination “stabilizes the vitamin C and enhances its photoprotective effect.”
She doesn’t build her own formulas around one hero ingredient because, as she describes it, “skin ages in multiple dimensions at once: laxity, wrinkles, pigmentation, redness, and keratoses.” She created the Alexiades Classification Scale to grade each of those separately.
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“No single ingredient addresses all of them,” she says. “It is also why my formulas contain 37 classes of actives, the MA37 complex, at high concentrations.” It’s also why she prefers a daily regimen to in-office treatments. “A procedure has historically treated one dimension at a time, while a well-designed regimen can address them all, every day.”
How to Read Skincare INCI Lists (And What Labeling Rules Hide)
Shoppers have gotten good at reading ingredient lists, but Macrene says those lists reveal “less than people think.”
“Ingredients are listed in descending order of concentration only down to about 1 percent,” she notes. “After that, the order can be anything.” Even a well-ordered list leaves out a lot. “The list tells you what is in the bottle, not how much, in what form, at what pH, or how stable it is.”
“The ingredients are listed in INCI format, which often conceals the origin of an ingredient,” she continues. “Additionally, an ingredient can appear on the label at a token amount that has no effect. The label is where you start asking questions, not where you find the answers.”
Formulation vs. Ingredients: Why Product Penetration and pH Balance Matter
For Macrene, “Vitamin C is the classic example. L-ascorbic acid needs a low pH to penetrate and oxidizes quickly when exposed to air and light, so the same ingredient in a poorly built formula in a clear jar is close to inert.”
“Retinoids and peptides depend on the form used, the concentration, the delivery system, and the vehicle,” she explains, and that’s “the difference between putting an ingredient on a label and formulating a product that works.” According to Macrene, “A retinoid at night and sunscreen in the morning is a combination every patient should follow.” She’s more careful about stacking actives. “Layering a retinoid with strong exfoliating acids or benzoyl peroxide can damage the barrier, and benzoyl peroxide can degrade tretinoin.”
“Irritation is not a sign the product is working,” Macrene points out, “and in patients with deeper skin tones it can lead to lasting pigmentation.” So whether it’s PDRN, peptides, or the next ingredient to take over your feed, what matters isn’t that it’s on the label, but whether the formula can actually deliver it where it needs to go.
Dr. Macrene Alexiades, MD, PhD, FAAD, is a board-certified dermatologist and the founder and CEO of Macrene Actives.
