Cited skincare — every flag names its source, no upsell.

Quaternium-15

The formaldehyde-releasing preservative that has topped patch-test allergy rankings — the first label name to screen if you react.

What it does

It releases more formaldehyde than the other preservatives of its kind and has long topped North American patch-test lists for preservative allergy. Big brands have been phasing it out since the 2010s, so it’s more likely in older products and some rinse-offs. If you’ve reacted to formaldehyde or a similar preservative, look for this name first.

The EU’s ingredient database lists it as a preservative (holds back germs in the product).European Commission, CosIng (© European Union, CC BY 4.0) · uses put in plain words by Drop ↗

The evidence, graded

moderateFragrance, essential oils, denatured alcohol and certain preservatives (methylisothiazolinone, the formaldehyde-releasers) are the usual suspects on sensitive skin. In the patch-test data read here — patients whose dermatitis was linked to a cleanser — the preservative quaternium-15 topped the list at 11.2% and fragrance mix I came fifth at 7.7%. Test a new product on a small patch of skin before you use it on your face.Warshaw 2018 · 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

Browse all 1238 ingredients — grouped by what they do, each with whatever evidence we can cite.

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