Formaldehyde releasers in skincare: allergy and the rules

What formaldehyde releasers are

A 2022 clinical review names five main formaldehyde releasers: quaternium-15, diazolidinyl urea, DMDM hydantoin, imidazolidinyl urea and 2-bromo-2-nitropropane-1,3-diol (bronopol). It says these ubiquitous preservatives are still often present, and sometimes undeclared, in cosmetics, medicines, medical devices, household detergents and industrial products.¹

Formaldehyde releasers are preservatives that give off formaldehyde, which is why allergy to formaldehyde and to the releasers overlap: a 2022 review advises that people sensitised to formaldehyde should avoid both.¹

How common allergy is

A 2010 review reported low frequencies of sensitisation in Europe: bronopol 0.4 to 1.2%, diazolidinyl urea 0.5 to 1.4%, imidazolidinyl urea 0.3 to 1.4% and quaternium-15 0.6 to 1.9%, with no recent data for DMDM hydantoin. Rates were far higher in the USA, where about 20% of cosmetics and personal care products contained a formaldehyde releaser.²

A Danish study of 8,463 patients patch-tested at one hospital department over ten years found that 1.5% had contact allergy to formaldehyde at the 1% test strength, with a decreasing trend, and 2.4% at the 2% strength. Quaternium-15 was the releaser most often positive, at 0.86%. About 36% of formaldehyde-allergic patients also reacted to a releaser, and almost 63% used products that released formaldehyde, with cosmetics the most common source.³

The 2022 review adds that these preservatives still readily cause localised (face or hand), airborne and generalised dermatitis. If someone is sensitised to formaldehyde, both formaldehyde and its releasers should preferably be avoided.¹

What the rules say

Snifff's summaries above describe an EU warning when free formaldehyde passes 10 ppm and a 0.2% cap on quaternium-15, and say India has no equivalent. A 2022 review says that in Europe the use of free formaldehyde and quaternium-15 in cosmetics is forbidden, and that contact allergy rates have been stable or decreasing.¹ In the Cosmetics Regulation, the ‘releases formaldehyde’ warning applies above 0.001% (10 ppm) of released formaldehyde, and both formaldehyde and quaternium-15 are listed in Annex II as prohibited substances.⁴

Rules for these preservatives have changed over time and the Annex entries above are from the consolidated legal text of 1 September 2025, so where Snifff’s summaries differ from them, the legal text is the authority. The Danish authors argue that better regulation of free formaldehyde and direct labelling are still warranted.³

Formaldehyde releasers in pregnancy and breastfeeding

Snifff's notes are cautions, and for formaldehyde itself, an instruction to avoid: formaldehyde is a known human carcinogen, and the releasers release it. We did not find pregnancy studies of these preservatives as used in cosmetics, so the caution rests on that carcinogen status and on precaution.

The documented harm from these preservatives is allergy rather than cancer, and the research on that is solid.^1,3 If you are pregnant or breastfeeding and want to avoid them, they are named plainly on most labels.

Evidence on cosmetic products in pregnancy is limited overall, so ask your doctor or midwife about the specific product you use.⁵

What you will see on the label

The names to look for are DMDM Hydantoin, Quaternium-15, Imidazolidinyl Urea, Diazolidinyl Urea or Formaldehyde. In Snifff, all five reads as High risk. For the rest of the formula, see what the score means and how to read the list.

As Snifff shows it

Formaldehyde releasers

DMDM Hydantoin

High risk

Pregnancy and nursing

Use with caution during pregnancy and lactation: this preservative releases formaldehyde, a known human carcinogen.

Regulatory gap

The EU requires a "releases formaldehyde" warning above 10 ppm of total free formaldehyde. India has no equivalent aggregate threshold.

Quaternium-15

High risk

Pregnancy and nursing

Use with caution during pregnancy and lactation: this preservative releases formaldehyde, a known human carcinogen.

Regulatory gap

The EU caps quaternium-15 at 0.2% and requires formaldehyde-release labelling. India has no equivalent warning.

Imidazolidinyl Urea

High risk

Pregnancy and nursing

Use with caution during pregnancy and lactation: this preservative releases formaldehyde, a known human carcinogen.

Regulatory gap

The EU requires a "releases formaldehyde" warning above 10 ppm of total free formaldehyde. India has no equivalent warning.

Diazolidinyl Urea

High risk

Pregnancy and nursing

Use with caution during pregnancy and lactation: this preservative releases formaldehyde, a known human carcinogen.

Regulatory gap

The EU requires a "releases formaldehyde" warning above 10 ppm of total free formaldehyde. India has no equivalent warning.

Formaldehyde

High risk

Pregnancy and nursing

Avoid during pregnancy and lactation: formaldehyde is a known human carcinogen.

Wording as it appears in the extension, which can change between releases.