What is it?
A natural acid found in lemons, limes and other citrus fruits, and a normal product of metabolism in plants and animals. Nearly all commercial citric acid is made by fermenting sugar with a mold and then recovering and purifying the acid. In cosmetics and personal care products it adjusts pH, binds trace metals so formulas stay stable, and is used as a fragrance ingredient. It is also one of the most widely used food acids.
Key information
- The CIR Expert Panel concluded that citric acid is safe in cosmetics in the present practices of use and concentration.
- In the products the panel reviewed, it was used at up to 4 percent in leave-on products and 10 percent in rinse-off products.
- The FDA lists citric acid as generally recognized as safe (GRAS) in food, with no limit other than good manufacturing practice.
- It is made by fermentation with a mold, but the acid is recovered from the fermentation liquid and purified to food-grade specifications.
More information
Citric acid can be extracted from citrus fruit, but the Cosmetic Ingredient Review (CIR) report notes that more than 99 percent of the world’s supply is made by microbial fermentation, historically using the mold Aspergillus niger grown on sugar sources such as molasses. The acid is then separated from the fermentation liquid and purified to meet food-grade specifications.
The CIR Expert Panel reviewed citric acid together with its salts and esters and concluded that they are safe in the present practices of use and concentration. Citric acid was reported in 6,795 cosmetic products, at up to 4 percent in leave-on products, 10 percent in rinse-off products and 39 percent in products diluted in the bath. In human tests it did not irritate skin at up to 5 percent, and a repeat patch test at 4 percent showed neither irritation nor allergy. Much stronger creams, at 20 percent and above, caused visible skin irritation in one study.
Two worries circulate online. One is that citric acid is “made from mold.” A 2018 report of four patients suggested manufactured citric acid might trigger inflammatory reactions, but its authors wrote that they “cannot conclusively affirm” it was the cause and called for controlled studies. The other is sun sensitivity: citric acid is an alpha hydroxy acid (AHA), and Health Canada sets conditions and warnings for AHA products at 3 percent and above. The CIR panel concluded that the concerns tied to AHAs such as glycolic acid do not apply to citric acid, which is chemically distinct.
Reality check: at the levels used to balance pH, citric acid is considered low risk. Products that use acids to exfoliate are a different case and may carry a sunburn alert on the label.
Sources: Cosmetic Ingredient Review: Final report on the safety assessment of citric acid, inorganic citrate salts, and alkyl citrate esters (2012); 21 CFR 184.1033: Citric acid (via Cornell LII); Health Canada: Cosmetic Ingredient Hotlist; Toxicology Reports (2018): Potential role of the common food additive manufactured citric acid in eliciting significant inflammatory reactions, a series of four case reports
