Bronopol

Tolerability and safety

Irritation potential

Medium

Allergen risk

High

Pregnancy

Caution

Use with caution

Sensitive

Releases formaldehyde

This is a formaldehyde-releasing preservative: it slowly gives off small amounts of formaldehyde in the water phase. If you are allergic to formaldehyde or have very sensitive skin, choose a product without it. At permitted levels the risk for everyone else is low. When several such preservatives are combined, their formaldehyde adds up – that matters more than any single one.

About this ingredient

Bronopol (2-bromo-2-nitropropane-1,3-diol) is a synthetic preservative with a bromine atom and a nitro group in its structure. Highly effective against gram-negative bacteria, especially Pseudomonas aeruginosa. Mechanism. Oxidises thiol (-SH) groups of key bacterial enzymes and blocks metabolism. Additionally slowly releases formaldehyde in aqueous medium (formaldehyde donor) – part of the antimicrobial effect comes from that. Where applied. Shampoos, shower gels, creams, micellar waters, shaving products. EU concentration cap – 0.1% leave-on and rinse-off (EU Cosmetics Regulation Annex V, entry 21). In Spain mostly mass-market (Mercadona, Carrefour Beauty), less common in dermocosmetics (which use gentler preservatives). Safety. The main issue is allergic contact dermatitis. Per NACDG 2019 and Cohen 2020, bronopol is in the top 10 cosmetic contact allergens (2.5–4% positive patch tests). Cross-sensitisation with other formaldehyde releasers (diazolidinyl urea, imidazolidinyl urea, DMDM hydantoin). Controversies. EU and SCCS reviewed further restrictions on formaldehyde releasers. As of May 2026 the 0.1% limit is unchanged, but many brands drop bronopol in favour of phenoxyethanol, dehydroacetate, and benzyl alcohol. Pregnancy – use with caution. Formaldehyde is a confirmed reproductive toxicant at high doses. At cosmetic 0.1% topical systemic absorption is low, but AEMPS and SEGO 2023 recommend avoiding without necessity. Contraindicated in eczema and allergic contact dermatitis. Lactation – with caution, especially on breast skin. Realistic assessment. An effective but sensitising preservative. Modern dermocosmetics uses safer alternatives. If you have eczema, allergic contact dermatitis, or sensitive skin, choose products with phenoxyethanol and benzyl glycol over bronopol. This is a formaldehyde-releasing preservative: in the water phase it slowly gives off small amounts of free formaldehyde. If you are allergic to formaldehyde or have very sensitive skin, choose a product without it – at permitted levels the risk for everyone else is low. When several such preservatives are combined, their formaldehyde adds up, and in the EU a total above 0.001% requires a "releases formaldehyde" label. Bronopol is a nitrosating agent: next to secondary or tertiary amines (DEA, TEA and derivatives) it can form carcinogenic nitrosamines. On its own at the permitted level (up to 0.1%) it is allowed, but pairing it with such amines is undesirable. In the EU bronopol carries an explicit condition to "avoid nitrosamine formation".

Frequently asked questions