Caprylhydroxamic Acid
Also known as N-Hydroxyoctanamide, Octanohydroxamic acid, CHA
“CIR Expert Panel says: safe as used in cosmetics.”
Caprylhydroxamic acid (CAS 7377-03-9; N-hydroxyoctanamide) is a newer-class preservative booster and chelating agent used in cosmetics at up to 0.3% (leave-on and rinse-off products). The CIR Expert Panel for Cosmetic Ingredient Safety conducted a dedicated safety assessment and issued a Final Report in October 2020 concluding the ingredient is safe in the present practices of use and concentration. The Panel reviewed genotoxicity data (largely negative), dermal absorption data, inhalation exposure in aerosol products (judged not a significant route of systemic exposure), and a QRA yielding a NESIL of 1056 µg/cm². A key clinical concern is sensitization potential on damaged or compromised skin: Ackermann et al. (Contact Dermatitis 2017, PMID 28421670) documented an epidemic of allergic contact dermatitis in Finland following reformulation of a moisturizer to include CHA, with positive patch test reactions at concentrations as low as 0.01% in compromised-skin patients; normal-skin controls tested negative. A 2025 update (PMID 40673532) revisiting the CIR assessment was also identified.
Effective preservative booster with chelating and antimicrobial activity at low concentrations (0.075–0.3%), enabling reduced total preservative loads
Valued as a paraben-free and formaldehyde-free preservation option for 'clean beauty' formulations
CIR Expert Panel concluded safe as used in cosmetics (Final Report, October 2020) — unconditional S finding with no concentration cap imposed
Works synergistically with phenoxyethanol, caprylyl glycol, and ethylhexylglycerin to broaden antimicrobial spectrum
- · Reported as cause of an epidemic of allergic contact dermatitis in Finland when a moisturizer was reformulated with CHA as a preservative alternative
- · CIR Panel noted genotoxicity data were largely negative but carcinogenicity data were absent; lack of structural alerts mitigated carcinogenicity concern
- · CIR Panel flagged that QRA did not account for penetration enhancers or damaged skin; manufacturers must consider this upon formulation
Sensitization potential on damaged or compromised skin: positive patch test reactions at ≥0.01% in Finnish patients with compromised-skin conditions (Ackermann et al. 2017, PMID 28421670); normal-skin controls did not react
Safety Assessment of Caprylhydroxamic Acid as Used in Cosmetics — CIR Final Report (Panel Meeting September 14–15, 2020; published Octobe…
“The Expert Panel for Cosmetic Ingredient Safety concluded that Caprylhydroxamic Acid is safe in cosmetics in the present practices of use and concentration described in this safety assessment.”— caphyd092020FR.pdf, p. 10