Caprylhydroxamic Acid in Hair and Skin Products: What It Is and Safety

Caprylhydroxamic acid is a preservative and chelating ingredient in cosmetics, not a hair-growth ingredient. We found no study of it on hair. The research that exists is about safety, including an outbreak of contact allergy from moisturizers that contained it.

Here's what it is, what safety reviews and allergy reports say, and what to do if a product irritates your scalp.

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Key Takeaways

• Caprylhydroxamic acid functions as a chelating agent in cosmetics.
• The Cosmetic Ingredient Review panel concluded it is safe in cosmetics at present use and concentration, while cautioning against use that increases penetration.
• In 2016, an outbreak of allergic contact dermatitis in Finland was traced to caprylhydroxamic acid in moisturizers.
• We found no study of caprylhydroxamic acid for hair.

What Is Caprylhydroxamic Acid?

Caprylhydroxamic acid is a cosmetic ingredient reported to function as a chelating agent. It's also used as a preservative alongside other ingredients such as phenoxyethanol.

Does It Do Anything For Hair?

It isn't a hair-growth ingredient. On a label it is a formulation ingredient, reported as a chelating agent and used in preservative mixtures, not a hair-growth active.

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If A Product Irritates Your Scalp

• Stop using the product.
• See a dermatologist if the reaction persists. Patch testing can identify the allergen.
• Avoid using products on damaged or broken skin.

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What The Research Shows

Safety Assessment

The Expert Panel for Cosmetic Ingredient Safety assessed caprylhydroxamic acid and noted it functions as a chelating agent. Positive sensitization results from a moisturizer containing it appeared to correlate with use on damaged skin, so the panel cautioned against use that would increase penetration. Using a quantitative risk assessment, it concluded the ingredient is safe in cosmetics in the present practices of use and concentration (Fiume et al., 2025).

The Finnish Outbreak

In 2016, dermatologists in Finland suspected contact allergy in patients using Apobase moisturizers after a formula change added a preservative mixture of phenoxyethanol, caprylhydroxamic acid and methylpropanediol. Of 39 patients patch tested, positive reactions were found to the new formulas and to caprylhydroxamic acid, but not to the old formulas, methylpropanediol or phenoxyethanol. The authors identified caprylhydroxamic acid as a new contact allergen (Ackermann et al., 2017).

A Growing Allergen

A 2025 paper was titled "Caprylhydroxamic Acid: A Growing Allergen in Skincare Products" (Theret et al., 2025). The PubMed record has no abstract, so we only report the title.

Propanediol is another common cosmetic ingredient we have reviewed; see propanediol in hair products.

Another preservative we have reviewed is DMDM hydantoin.

See also: Lecithin for Hair: What the Research Shows

Frequently Asked Questions

Does caprylhydroxamic acid help hair?

We found no study showing that it does. It is a cosmetic ingredient with a chelating or preservative role.

Is caprylhydroxamic acid safe?

A cosmetic safety panel found it safe at present use levels, but allergic contact dermatitis has been reported. See a doctor if a product irritates your skin.

Can it cause an allergic reaction?

Yes, in some people. It was identified as a contact allergen in a Finnish outbreak.

References

1. Fiume MM, Bergfeld WF, Belsito DV, et al. Safety Assessment of Caprylhydroxamic Acid as Used in Cosmetics. Int J Toxicol. 2025. PubMed
2. Ackermann L, Virtanen H, Korhonen L, et al. An epidemic of allergic contact dermatitis caused by a new allergen, caprylhydroxamic acid, in moisturizers. Contact Dermatitis. 2017. PubMed
3. Theret V, Burle E, Giordano F. Caprylhydroxamic Acid: A Growing Allergen in Skincare Products. Contact Dermatitis. 2025. PubMed