← The FormularySkin & faceGluconolactone
Also known as PHA, polyhydroxy acidThe gentlest acid on the shelf, which is the entire point of it.
PHAs exist because AHAs are too much for a lot of people. The bigger molecule penetrates more slowly, so you get gentler exfoliation and far less stinging, at the cost of speed. If your skin tolerates glycolic or lactic acid you will get more from those. If it does not, this is the sensible compromise rather than a lesser one.
A polyhydroxy acid — a larger, slower cousin of glycolic acid, used where stronger acids would sting.
Weakens the bonds holding dead cells at the surface so they shed on schedule instead of accumulating. It also holds water, which is why it tends not to leave skin tight.
Loosens dead surface cells gradually, which over time makes tone look more even.
Reactive skin, or anyone who has tried an AHA and regretted it.
Once daily on clean skin, with sunscreen every morning. Introduce it separately from retinol.
Smoother texture over weeks and more even-looking tone over months. No immediate change.
Grade B as an exfoliant. In comparative studies it matched an AHA regimen for photoaging with less irritation, and unlike AHAs it did not increase sun sensitivity — one of the few claims in this category the evidence actually supports.
Read the labelUnlike glycolic acid, it has not been shown to increase sun sensitivity. Wear sunscreen daily anyway — that advice does not depend on what is in your serum.
Evidence grades describe how well an ingredient is studied — A well-supported, C emerging — not a promise of results. Educational, not medical advice. Doses are typical ranges; follow the label on the product.