Quaternium-15
What It Is
Quaternium-15 (methenamine 3-chloroallylochloride) is a synthetic preservative in the formaldehyde-releasing preservative class (CAS 4080-31-3). It is a quaternary ammonium salt that releases formaldehyde as its antimicrobial mechanism. Quaternium-15 releases more free formaldehyde per unit weight than most other FRPs, which makes it both one of the most effective and most controversial preservatives in this category.
Common Uses
Quaternium-15 was historically used in shampoos, conditioners, lotions, cosmetic creams, and some household products. Its use has declined significantly due to its high formaldehyde release rate and regulatory action. The EU banned quaternium-15 in cosmetic products in 2017. It remains permitted in the United States, though many manufacturers have voluntarily reformulated to remove it. Quaternium-15 is still used in some industrial applications where formaldehyde release is less concerning.
How It Works
Quaternium-15 releases formaldehyde through hydrolysis -- the methenamine portion of the molecule breaks down in aqueous solution to release formaldehyde. It releases approximately three times more free formaldehyde than DMDM hydantoin at equivalent concentrations (de Groot and Bos, 1996). The released formaldehyde then cross-links microbial proteins to provide broad-spectrum preservation. The quaternary ammonium portion of the molecule may also contribute some independent antimicrobial activity.
Safety and Regulation
The EU banned quaternium-15 in cosmetic products effective 2017, citing formaldehyde release and sensitization concerns (Commission Regulation (EU) 2017/1410). It was the first commonly used FRP to be specifically banned by the EU rather than merely restricted.
Quaternium-15 is one of the most frequently positive allergens on standard patch-testing panels. Contact allergy rates in consecutively tested dermatology patients range from 5% to 9% depending on the study population (Warshaw et al., 2015). Some of this allergy is attributed to formaldehyde sensitivity (since quaternium-15 releases formaldehyde), but quaternium-15 itself is also a distinct sensitizer independent of its formaldehyde release.
In the United States, the CIR Expert Panel concluded quaternium-15 is safe at concentrations up to 0.2% when formulated to not exceed safe formaldehyde levels (CIR, 2006). The FDA has not restricted its use.
Why Natural Flower Power Does Not Use It
Natural Flower Power does not use quaternium-15 in any product.
Quaternium-15 releases the most formaldehyde of any commonly used FRP and has been banned in EU cosmetics -- both facts that make it incompatible with our formulation standards. Even in the US market where it remains permitted, using an ingredient that has been specifically banned by the EU's cosmetic regulatory framework would undermine the trust our customers place in our ingredient choices. Our BIT-based preservation system requires no formaldehyde release and operates at concentrations far below those that would cause sensitization concerns.
Related Ingredients
Formaldehyde is the active substance released by quaternium-15. DMDM hydantoin is a less aggressive FRP that releases less formaldehyde per unit weight. Imidazolidinyl urea and diazolidinyl urea are other FRPs. Benzisothiazolinone (BIT) is the preservative Natural Flower Power uses instead.
Sources
- de Groot, A.C., and Bos, J.D. "Formaldehyde-Releasers: Relationship to Formaldehyde Contact Allergy." Contact Dermatitis, vol. 34, no. 4, 1996, pp. 243-250.
- Warshaw, E.M., et al. "Patch Testing with NACDG Standard Series." Dermatitis, vol. 26, no. 1, 2015, pp. 49-59.
- European Commission. Commission Regulation (EU) 2017/1410.
