What is it?
A synthetic thickener made by polymerizing acrylic acid and crosslinking the chains into a very large network. Carbomer does not dissolve in water but swells greatly, and it is used to turn water-based products into gels and to thicken and stabilize lotions and creams. It is the most widely used of the acrylate polymers in cosmetics, listed in more than 6,000 products in 2018, and it is also used in medicines.
Key information
- The CIR Expert Panel found carbomer safe as used in 1982 and, in a 2018 review, safe when formulated to be non-irritating, and it stipulated that such polymers should not be made using benzene.
- Some grades have been made with benzene, a known human carcinogen, as the polymerization solvent; the FDA has told drug makers to switch to benzene-free grades.
- US Pharmacopeia standards for benzene-free carbomers limit benzene to 2 ppm; the older standards for benzene-process grades allowed up to 5,000 ppm.
- Ingredient labels do not show which kind of carbomer was used.
More information
Carbomer is made by polymerizing acrylic acid in a solvent together with a small amount of a crosslinking agent, producing an enormous molecule that swells in water, up to 1,000 times its dry volume, rather than dissolving. When the European Food Safety Authority (EFSA) evaluated a carbomer made in ethyl acetate as a proposed food additive in 2021, it found no evidence that it is absorbed from the gut and no genotoxicity concern, and it set an acceptable daily intake of 190 mg per kilogram of body weight. It did recommend a lower limit for leftover acrylic acid.
The Cosmetic Ingredient Review (CIR) Expert Panel first found carbomers safe in 1982, noting low potential for skin irritation and allergy in human tests, and reaffirmed that in 2003. In 2018 it assessed carbomer again together with 125 other acrylate polymers, including sodium polyacrylate, and concluded they are safe when formulated to be non-irritating.
The real issue is how some carbomer is made. Certain grades are polymerized in benzene, a known human carcinogen. The CIR has called attention to benzene as an impurity in carbomer, and in 2018 it stipulated that these polymers should not be polymerized in benzene, because some benzene can stay trapped in the polymer. In 2023 the FDA told drug manufacturers to switch to carbomers made without benzene: the older US Pharmacopeia standards for benzene-process grades allowed up to 5,000 ppm, compared with 2 ppm for benzene-free grades. Those older standards were dropped as of August 1, 2026. These steps apply to medicines, not cosmetics.
Reality check: carbomer itself is considered low risk as used. The open question is leftover benzene from benzene-based manufacturing, which an ingredient label cannot reveal.
Sources: Cosmetic Ingredient Review: Amended safety assessment of acrylates copolymers as used in cosmetics, final amended report (2018); FDA: Reformulating drug products that contain carbomers manufactured with benzene, guidance for industry (2023); USP-NF: Omission of the Carbomer 934, 934P, 940, 941 and 1342 monographs, official August 1, 2026; EFSA Journal (2021): Safety evaluation of crosslinked polyacrylic acid polymers (carbomer) as a new food additive
