What is it?
A fruit acid best known for the tart taste of apples, especially unripe ones, and a normal part of metabolism in plants and animals. Commercial malic acid is made either from fumaric acid, giving the natural L-form, or from maleic acid, giving DL-malic acid, a mix of the natural form and its mirror image. In cosmetics it is mainly used in small amounts to adjust pH, and also as a fragrance ingredient.
Key information
- The CIR Expert Panel concluded in 2022 that malic acid is safe in cosmetics in the present practices of use and concentration.
- Its highest reported leave-on use was 2.1 percent, in a hair spray.
- The FDA lists malic acid as generally recognized as safe (GRAS) in food, except baby food.
- Health Canada groups malic acid with the alpha hydroxy acids (AHAs), with conditions for products that contain 3 percent or more.
More information
Malic acid is an intermediate in the citric acid cycle, the pathway cells use to make energy, and its L-form occurs naturally in fruits. The DL-form does not occur in nature; it is made from maleic acid, which in turn is produced from benzene. Manufacturers purify malic acid to limit leftover maleic and fumaric acids, by-products of production.
The Cosmetic Ingredient Review (CIR) Expert Panel first reviewed malic acid in 2001 and found it safe as a pH adjuster, but lacked data for other uses. In an amended review published in 2022, prompted by growing use, it concluded that malic acid and sodium malate are safe in the present practices of use and concentration. Reported uses rose from 47 in 1998 to 228 in 2018. The highest leave-on concentration was 2.1 percent, and products diluted in the bath contained up to 50 percent. The panel said the only significant toxic effect was skin and eye irritation from its acidity, which is minimized when it is used to adjust pH, and a repeat patch test at 1 percent found no allergic reactions. It advised limiting eye exposure to hair sprays that contain it.
In food, the FDA allows malic acid as a flavoring agent, flavor enhancer and pH control agent, but not in baby food. Health Canada classes it as an alpha hydroxy acid (AHA), like citric and glycolic acids, and sets conditions and warnings for AHA products at 3 percent and above. Those cautions are aimed at exfoliating products; the small amounts used to balance pH are a different case. On labels, look for malic acid or its salt, sodium malate.
Sources: Cosmetic Ingredient Review: Amended safety assessment of malic acid and sodium malate as used in cosmetics (International Journal of Toxicology, 2022); 21 CFR 184.1069: Malic acid (via Cornell LII); Health Canada: Cosmetic Ingredient Hotlist
