What is it?
The acid that gives vinegar its sour taste and sharp smell. Vinegar is a dilute solution of acetic acid, typically 5 to 8 percent. Acetic acid occurs naturally in plant and animal tissues, and it is also made synthetically on an industrial scale. In cosmetics and hair products it is used in very small amounts to adjust pH and as a fragrance ingredient. It is also a common food acid, listed as E260.
Key information
- Acetic acid is the acid in vinegar, which typically contains 5 to 8 percent of it.
- The CIR Expert Panel concluded that acetic acid is safe in the present practices of use and concentration in cosmetics, where reported levels were 0.3 percent or less.
- Concentrated acetic acid is corrosive, and in a human patch test a 10 percent solution irritated most volunteers.
- The FDA affirms acetic acid as generally recognized as safe (GRAS) as a food ingredient.
More information
Industrial acetic acid is made by several synthetic routes, including reacting methanol with carbon monoxide and oxidizing acetaldehyde or butane. The Cosmetic Ingredient Review (CIR) Expert Panel assessed it together with its salts and a group of acetate esters, because enzymes in the skin break those esters down into acetic acid. The panel concluded that all of them are safe in the present practices of use and concentration, in a final report published in 2012. In the data it reviewed, acetic acid was reported in 11 products, at 0.0003 to 0.3 percent, in items such as hair dyes, nail polish and bath soaps.
With acids, strength is what matters. Nearly pure (“glacial”) acetic acid destroyed guinea pig skin after 24 hours of contact, and solutions stronger than 10 percent caused severe, permanent eye injury in rabbits. Even a 5 percent solution, about the strength of vinegar, caused severe but reversible eye injury in rabbits. In a human patch test, 10 percent acetic acid irritated 70 to 94 percent of volunteers, depending on the laboratory. Workers exposed to strong solutions or vapor can have eye, skin, nose and throat irritation and burns. Reported cosmetic levels were at most 0.3 percent.
In food, the FDA affirms acetic acid as generally recognized as safe (GRAS) for uses such as pickling, flavoring and pH control. On labels it appears as acetic acid; in foods it may be listed as E260. Its salts, such as potassium acetate and sodium acetate, were covered by the same CIR conclusion.
Sources: Cosmetic Ingredient Review: Methyl acetate, simple alkyl acetate esters, acetic acid and its salts, draft final report (2010); Cosmetic Ingredient Review: Quick reference table of ingredient findings (September 2020); Code of Federal Regulations, 21 CFR 184.1005 (via Cornell LII): Acetic acid; CDC/NIOSH Pocket Guide to Chemical Hazards: Acetic acid
