What is gluconolactone? The gentle acid in our dark spot serum

Short answer: gluconolactone is a polyhydroxy acid, or PHA. It's part of the same broad family as glycolic and lactic acid, but it's a much larger molecule, and it's usually described as the gentler member of that family. It's one of the actives in our Dark Spot Serum for Sensitive Skin. Below we explain what it is, what researchers have studied, and what that research does and doesn't tell you.

Key takeaways

• Gluconolactone is a polyhydroxy acid (PHA). Alpha-hydroxy acids (AHAs) like glycolic and lactic acid are its better-known cousins.
• It's a far bigger molecule than glycolic acid: about 178 g/mol against 76 g/mol.
• Most published research on it tested finished formulas rather than gluconolactone alone, and a lot of that research came from the company that developed PHAs for skincare.
• In our serum, gluconolactone sits alongside mushroom extracts instead of the brightening acids, like kojic acid, that this category usually uses.

What is gluconolactone?

Gluconolactone is a polyhydroxy acid. In chemistry terms, it's the lactone (ring) form of gluconic acid, which comes from glucose. "Poly" means it carries several hydroxyl groups, where the simpler alpha-hydroxy acids have one.

You'll find it on ingredient lists as gluconolactone. It shows up in formulas aimed at people who want an acid in their routine without reaching for the strongest one on the shelf.

How is it different from glycolic acid?

The clearest difference is size. Glycolic acid is the smallest of the common skincare acids, at about 76 g/mol. Gluconolactone is more than twice that, at about 178 g/mol. That size difference is the main reason PHAs are usually discussed as the gentler option, since larger molecules move into skin more slowly.

Researchers have compared PHA and AHA skincare regimens directly. Among them, a 2004 paper by Edison and colleagues set a PHA regimen against an AHA regimen (reference 2 below).

What does the research show?

The research is modest, and we'd rather tell you that up front:

• In two 12-week studies published in 2004, dermatology researchers reported that skincare formulas containing gluconolactone were well tolerated with once-daily use (reference 1).
• Those studies tested finished products, which combined gluconolactone with other actives. They did not test gluconolactone on its own.
• Much of the PHA research was carried out by researchers connected to the company that developed PHAs for skincare. That doesn't make it wrong, but it's worth knowing.

What the research doesn't show

None of the studies above tested our serum. We haven't run a clinical study on it, and we won't suggest otherwise. We include gluconolactone because of its reputation as a gentle acid. The serum is built to be used as part of a regular routine, not to deliver an overnight change.

Why it's in our Dark Spot Serum

Most dark spot serums lean on brightening acids. Ours doesn't contain typical brightening acids such as kojic acid. It pairs gluconolactone with Shiitake, Turkey Tail and Jackfruit extracts, plus soothing botanicals including sea fennel and calendula. It's fragrance free and formulated for sensitive skin.

A note on the mushrooms: research on these extracts so far is early-stage lab work, not human studies. We'll cover that in its own post.

See the Dark Spot Serum for Sensitive Skin →

How to use it

Apply a small amount to clean, dry skin and massage until absorbed. It works in the morning or at night, after cleansing. In the morning, apply it before the Vitamin Glow Serum. As with any new product, patch test first, and stop using it if irritation occurs.

FAQ

Is gluconolactone an exfoliant?
It belongs to the same family of acids used for exfoliation. Its larger size is why it's generally described as milder than glycolic acid.

Can I use it with retinol?
Many routines keep acids and retinol in separate steps or at different times of day. In ours, retinol goes on at night. If you're new to either one, introduce one product at a time.

Does a gentler acid mean it does less?
It means a different approach. If your skin already does well with glycolic acid, you may not need a PHA. PHAs are a common choice for people who've found stronger acids too much.

Do I still need sunscreen?
Yes. Daily SPF belongs in every morning routine, whatever serums you use.

References

1. Grimes PE, Green BA, Wildnauer RH, Edison BL. The use of polyhydroxy acids (PHAs) in photoaged skin. Cutis. 2004;73(2 Suppl):3–13.
2. Edison BL, Green BA, Wildnauer RH, Sigler ML. A polyhydroxy acid skin care regimen provides antiaging effects comparable to an alpha-hydroxyacid regimen. Cutis. 2004;73(2 Suppl):14.

Elyserra sells the Dark Spot Serum mentioned in this article. This article is for general information and isn't medical advice. If you have a skin concern, talk to a dermatologist.