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Mandelic acid

Mandelic acid is an alpha hydroxy acid (AHA) with a ring structure, a larger molecule than glycolic acid. It exfoliates the skin surface like other AHAs and is generally described in the literature as acting more slowly and more mildly. Like every AHA, it calls for daily sun protection.

At a glance

  • Evidence level A. Published research on the ingredient itself.
  • What it is. An aromatic alpha hydroxy acid, first isolated from bitter almond extract.
  • What it does. Surface exfoliation, with a slower, gentler profile than glycolic acid in the literature.
  • Caution. Increases sun sensitivity. Use sunscreen daily while using it and for a week afterwards.

What it is

Mandelic acid takes its name from the German Mandel, almond. It was first obtained by heating an extract of bitter almonds with acid; cosmetic grades today are made synthetically. Chemically it is glycolic acid with a benzene ring attached, which makes the molecule larger and less water-loving than glycolic or lactic acid.

It is one of several alpha hydroxy acids used in skincare. As with all of them, concentration and the finished pH together set how strongly it acts. A percentage without a pH describes only half the formula.

What it does in skincare

Mandelic acid weakens the bonds that hold dead cells together in the outer layer of skin, so they detach more evenly. That is the same action as glycolic acid. The difference the literature points to is pace: a larger molecule is generally associated with a slower, milder action at the same strength.

That profile is why mandelic acid is often chosen for skin that finds glycolic acid too active, and why it appears in combination formulas with smaller acids. It is used in leave-on serums at low strength and in professional peels, often blended with other acids.

Evidence

The studies below describe the ingredient itself.

The research record on mandelic acid is smaller than for glycolic or lactic acid, and most studies are short and small. Kornhauser and colleagues reviewed the classification and actions of hydroxy acids, including mandelic acid, in 2010.

Jacobs and Culbertson measured facial skin elasticity with an instrument before and after a course of topical mandelic acid, in a small group of adults, and reported improved measurements. Wójcik and colleagues compared azelaic and mandelic acid peels in women and measured sebum on the skin surface.

In the literature on acne, Garg and colleagues compared glycolic acid peels with salicylic-mandelic acid peels in a comparative study of patients with active acne and post-acne marks. The study compared outcomes and tolerability between the two peel types. This is published literature on peels applied by clinicians.

Mandelic acid is an alpha hydroxy acid, so the sun sensitivity findings behind FDA's AHA guidance apply to the class. FDA's recommended label statement covers AHA cosmetics as a group.

Use and caution

Sun-sensitivity notice. FDA recommends this statement for cosmetics containing alpha hydroxy acids:

Sunburn Alert: This product contains an alpha hydroxy acid (AHA) that may increase your skin's sensitivity to the sun and particularly the possibility of sunburn. Use a sunscreen, wear protective clothing, and limit sun exposure while using this product and for a week afterwards.

Full guidance: acids and sun sensitivity.

  • Patch test first, especially if your skin reacts to other acids. See patch testing and declared allergens.
  • Start with a few evenings a week.
  • Stop if stinging persists or redness stays.
  • Avoid the eye area and broken skin.
  • Do not stack several exfoliating products in one routine without professional guidance.

Early bumps are often called "purging". What the term covers: the purging myth.

In Vegalab products

The Brightening NanoSerum sealed vial set lists mandelic acid together with glycolic acid and lactic acid. The sun-sensitivity notice above applies to it.

References

  1. Kornhauser A, Coelho SG, Hearing VJ. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clin Cosmet Investig Dermatol. 2010;3:135-142.
  2. Jacobs SW, Culbertson EJ. Effects of topical mandelic acid treatment on facial skin viscoelasticity. Facial Plast Surg. 2018;34(6):651-656.
  3. Wójcik A, Kubiak M, Rotsztejn H. Influence of azelaic and mandelic acid peels on sebum secretion in ageing women. Postepy Dermatol Alergol. 2013;30(3):140-145.
  4. Garg VK, Sinha S, Sarkar R. Glycolic acid peels versus salicylic-mandelic acid peels in active acne vulgaris and post-acne scarring and hyperpigmentation: a comparative study. Dermatol Surg. 2009;35(1):59-65.
  5. US Food and Drug Administration. Guidance for Industry: Labeling for Topically Applied Cosmetic Products Containing Alpha Hydroxy Acids as Ingredients. January 2005.
  6. Kaidbey K, Sutherland B, Bennett P, et al. Topical glycolic acid enhances photodamage by ultraviolet light. Photodermatol Photoimmunol Photomed. 2003;19(1):21-27.
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