Structural formula of Bronidox


What is it?

“Bronidox, or 5-bromo-5-nitro-1,3-dioxane, is an antimicrobial chemical compound. Bronidox causes inhibition of enzyme activity in bacteria.[3] Bronidox is corrosive to metals.” Wikipedia

What are the effects?

This substance belongs to the groups:

Bronidox is a preservative and a sister substance to Bronopol.

The main concern regarding this substance is that it is an effective nitrosating agent.  It means that bronidox could form toxic nitrosamines, if it is in the same products as ingredients containing amines. Bronidox + amines = nitrosamines.  Amines, such as ethanolamines, together with bronidox have been shown to form substantial amounts of nitrosamines after prolonged storage (50 days).

Bronidox may also, under specific conditions, decompose itself to formaldehyde. Even though it may be in small doses, the release of formaldehyde can certainly enhance the possibility of nitrosamine formation. Aldehydes, particulary formaldehydes, may catalyze the formation of nitrosamines.

The Scientific Committee on Consumer Safety (SCCS ) from the European Union writes that whenever this preservative is in the same products as other compounds containing secondary amines, “substantial nitrosamine formation is to be expected.”

The SCCS also concludes that “Tertiary amines are considerably less reactive, yet can give rise to some nitrosamine formation after extended periods of storage.  It is not known to what extent alkanolamides or substituted ureas might react but since their nitrosation by Bronopol/Bronidox cannot be ruled out, any co-formulation of these preservatives in cosmetics together with compounds having a nitrosatable nitrogen is to be avoided.”

If you want to limit the possibility of having unwanted nitrosamines in your products it is advisable to avoid buying products with Bronidox. This is because it can get problematic trying to find out which substances contain amine structures (bronidox + amines = nitrosamines).


Even though it is not listed on the content list, Bronidox may contain impurities from:

  • Formaldehyde – linked to cancer, damaged fertility and allergies
  • Nitrosamines – linked to cancer, endocrine disruption, organ system toxicity, developmental toxicity and damaged fertility.

How is it used?

Bronidox is used as a preservative in cosmetic products. It’s effective against yeast and fungi, and kills bacteria in cosmetics such as shampoos and other bath products.

We use the European Commissions definition of Cosmetics:
“Cosmetics range from everyday hygiene products such as soap, shampoo, deodorant, and toothpaste to luxury beauty items including perfumes and makeup”.

Did you find this ingredient in a product?

Comment and share with a link!