At a glance
| Chemical family | Bromonitro alcohol — preservative and formaldehyde releaser |
| CAS number | 52-51-7 |
| Classification | Not individually IARC classified. Releases formaldehyde (IARC Group 1 carcinogen). EU Cosmetics Regulation Annex V permits up to 0.1%. Contact allergen (both direct and via formaldehyde release) |
| Where you encounter it | Cosmetics (moisturisers, shampoos, body washes); cleaning products; industrial cooling water biocide; some pharmaceutical formulations; wet wipes |
| Sleep micro-environment relevance | Cosmetics containing bronopol applied before bed transfer to pillowcases. Cleaning product residues on bedroom surfaces. Releases formaldehyde into the product and from residues on skin/surfaces |
Regulatory & certification status
| European Union | Cosmetics Regulation Annex V permits bronopol up to 0.1% in cosmetic products. Products containing formaldehyde releasers must declare 'contains formaldehyde' above 0.05% free formaldehyde. CLP Acute Tox. 4, Eye Dam. 1, Skin Sens. 1. Regulatory |
| United States | CIR (Cosmetic Ingredient Review) assessed bronopol as safe up to 0.1% in cosmetics. No FDA-specific restriction. Labeling of formaldehyde releasers is not required in the US. Regulatory |
| Canada | Health Canada Cosmetic Ingredient Hotlist permits bronopol up to 0.1% in cosmetics. Labeling requirements apply. Regulatory |
| International | Not individually IARC classified. EU and Canada permit up to 0.1% in cosmetics. Formaldehyde-releaser labeling varies by jurisdiction. Regulatory |
What it is
Bronopol is a nitrobromoalcohol preservative effective against bacteria and some fungi. It was developed in the 1960s and became widely used in cosmetics and personal care products. Bronopol works through two mechanisms: direct antimicrobial activity and release of formaldehyde. The formaldehyde release has been a regulatory focus because formaldehyde is an IARC Group 1 carcinogen and a potent contact sensitizer. IARC has not evaluated bronopol individually. Bronopol is a contact allergen in its own right — patch test positivity rates range from 1-3% in dermatology clinic populations. It can also decompose to form nitrosamines under certain conditions (alkaline pH, presence of amines), though this is controlled by formulation pH management. The EU permits bronopol in cosmetics at up to 0.1% and requires products containing formaldehyde releasers above 0.05% to declare 'contains formaldehyde' on the label.
Where it shows up in bedding
Bronopol enters the bedroom through cosmetics applied before sleep — night creams, moisturisers, and body lotions that contain bronopol as a preservative. These products transfer to pillowcases and sheets during sleep, depositing bronopol residues on bedding. The formaldehyde that bronopol releases is present in the product and continues to be released from residues. For bronopol-sensitised individuals or those sensitive to formaldehyde, this overnight exposure pathway can maintain facial or contact dermatitis. Switching to bronopol-free and formaldehyde-releaser-free cosmetics eliminates this source.
Citations
- de Groot, A.C. and Veenstra, M. (2010). Formaldehyde-releasers in cosmetics in the USA and in Europe. Contact Dermatitis, 62(4): 221-224. Source Peer-reviewed
- EU Cosmetics Regulation (EC) No 1223/2009, Annex V — Preservatives. Source Regulatory
- ECHA. 2-Bromo-2-nitropropane-1,3-diol — Substance Information. Source Regulatory
Frequently asked questions
Does bronopol release formaldehyde?
Yes. Bronopol is classified as a formaldehyde releaser — it slowly decomposes in aqueous solution to release free formaldehyde, which provides additional antimicrobial activity. The amount of formaldehyde released depends on pH, temperature, and concentration. The EU requires cosmetics containing formaldehyde releasers to declare 'contains formaldehyde' if free formaldehyde exceeds 0.05%.
Can bronopol in my night cream cause skin problems?
If you are allergic to bronopol or formaldehyde, a night cream containing bronopol applied before sleep can cause or maintain facial contact dermatitis. The overnight occlusion on a pillowcase may intensify the reaction. A dermatologist can diagnose bronopol allergy through patch testing. Switching to a bronopol-free preservative system (phenoxyethanol, sorbate-based, or preservative-free) resolves the issue.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-08. If you find a factual error, contact us.