A cell biologist in Osaka on why the most exciting word in American skincare is already a legacy term in Seoul and Brussels, and what to ask instead.

45% of @cosme members would rather skip a product than feel it sting. Online, the US routine is 20% azelaic by day and tretinoin by night. Two definitions of the word works, and the skin biology under both. The first post with an evidence label on every section.

500 kDa is not 500 Da. What sponge spicules actually do to skin, why a PDRN fragment of 500,000 daltons cannot cross a 500 dalton door, and the 2020 meta-analysis the brand cites that I could not find. Four questions to ask before you pay.

Calecim’s own randomized, double-blind, split-face trial: blinded investigators saw no difference from the vehicle. What PTT-6 conditioned medium is, where the website’s percentages come from, and four questions to ask any stem cell cream.

Salmon DNA is on every shelf right now, and PDRN is 100 to 3,000 times too big to cross intact skin. Here is what a topical serum can actually do, what the injected version has behind it, and the one question to ask before you pay a premium.

The SPF on a foundation is a real number measured in a lab. The problem is the lab used four times more product than you will ever put on your face. Here is the arithmetic, the two models scientists argue about, and what to wear instead.

The viral Korean laser everyone is flying to Seoul for is often an Israeli, Italian or American machine. What the five device categories actually do, who makes them, and the two questions to ask before any treatment.

Cica is on every label right now, and most of it is noise. Here is what centella actually does for a stressed barrier, the concentration that has data behind it, and what is just makeup wearing a treatment costume.

Every serum promises peptides, and almost none will say which ones have human data. So here they are, ranked: two with real trials behind them, one oversold as topical Botox, and the rest still waiting for evidence.