#Acid

Polyglutamic acid vs hyaluronic acid: the new humectant with five times the holding capacity

A friend asked me last winter why her new polyglutamic acid serum, marketed as the “next-generation hyaluronic acid,” made her face feel…

The acid-plus-retinoid layering myth: pH math and the night-cycling alternative

TL;DR: The ‘never mix acids and retinoids’ rule originated from skin-cycling logic and from concern that the low pH needed for AHA…

Tranexamic acid: the prescription drug pharmacies sell over the counter in your serum

TL;DR: Tranexamic acid is a prescription antifibrinolytic drug, used in surgery to control bleeding, and used at five hundred to one thousand…

The mandelic acid case for darker skin tones

TL;DR: Mandelic acid has a molecular weight roughly twice that of glycolic, which sounds like a disadvantage and is actually the point.…

L-ascorbic acid degrades faster than the bottle admits

TL;DR: An open bottle of 15% L-ascorbic acid serum loses a meaningful percentage of its active dose within weeks, not months. The…