Cited skincare — peer-reviewed evidence, no upsell.

Quaternium-15

The formaldehyde releaser with the highest patch-test positivity of the class. Phased out of many formulas, but still on older labels.

What it does

Quaternium-15 releases more formaldehyde than the other releaser preservatives and has historically topped North American patch-test rankings for preservative allergy. Major brands have been phasing it out since the 2010s, so it turns up more in older formulations and some rinse-off products than in current leave-ons. If you have ever reacted to formaldehyde or to another releaser, this is the first label name to screen for. Not a concern for most users at preserved concentrations.

The evidence, graded

strongCommon sensitivity and contact-allergy triggers in skincare include fragrance (the most-cited cosmetic allergen), essential oils, denatured alcohol, and certain preservatives (methylisothiazolinone, formaldehyde-releasers). Patch test new products on the inner forearm for 48–72 hours before face-wide use.Warshaw 2020 · Dermatitis ↗

Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.

Also known as

Dowicil 200

This page is public and indexed on purpose (unlike profiles and drops, which are unlisted) — it’s the citation behind shared ingredient cards, and it should be findable.

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