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Quaternium-15

AvoidPreservativepreservative

Banned in EU cosmetics or credibly linked to serious harm.

Also written as: Methenamine 3-Chloroallylochloride · Dowicil 200 · cis-1-(3-Chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride

What it is

Quaternium-15 was a widely used formaldehyde-releasing preservative and, per unit of use, one of the most allergenic. It used to hold entry 31 on the EU list of permitted preservatives; that entry has been deleted, so it can no longer legally be used to preserve a cosmetic sold in the EU. It is still permitted in some other markets, including the United States, so imported products may contain it.

Worth knowing

  • One of the most clinically relevant formaldehyde-releasing allergens

    The 2026 meta-analysis found a pooled prevalence of 1.89% and the highest clinical relevance of any releaser at 55.67%, meaning when a patient tested positive, the reaction usually explained their actual dermatitis.

    Matters most toAnyone with formaldehyde or preservative allergy, and anyone buying skincare from outside the EU.

  • No longer legal in EU cosmetics

    It was removed from the EU list of permitted preservatives in 2019. A product on sale in the EU that lists it is non-compliant.

    Matters most toPeople buying imported or grey-market skincare online.

Where the EU stands

Banned in EU cosmetics

Prohibited in EU cosmetic products since 2019. Its former Annex V entry 31 has been deleted, and cosmetics may not contain preservatives that are not on the Annex V list.

Regulation (EC) No 1223/2009: former Annex V entry 31, deleted; prohibition effective 2019 (Commission Regulation (EU) 2019/831) · source ↗

Sources (2)

Every link goes to the original: a journal, a PubMed record or an EU document.

  1. [1]
    The Prevalence of Contact Allergy to Formaldehyde and Formaldehyde Releasers: A Systematic Review and Meta-Analysis

    Contact Dermatitis · 2026 · doi:10.1111/cod.70172

    Quaternium-15 had a pooled contact allergy prevalence of 1.89% and the highest clinical relevance of any formaldehyde releaser (55.67%); the review confirms it has been prohibited in EU cosmetics since 2019.

  2. [2]
    Contact dermatitis associated with preservatives: Retrospective analysis of North American Contact Dermatitis Group data, 1994 through 2016

    Journal of the American Academy of Dermatology · 2021 · doi:10.1016/j.jaad.2020.07.059

    Quaternium-15 tested at 2% in petrolatum produced positive reactions in 7.7% of patch-tested North American patients, among the highest rates recorded for any preservative.