Ingredient review
Bronidox
INCI: 5-BROMO-5-NITRO-1,3-DIOXANE
An effective but controversial preservative that is now banned in the EU and restricted elsewhere due to potential skin irritation and nitrosamine formation.
In plain English
5-Bromo-5-nitro-1,3-dioxane is a synthetic preservative that stops bacteria and fungi from growing in cosmetic products. It was once common in shampoos and body washes, but it has been linked to skin irritation and can form nitrosamines, which are potentially harmful compounds. Because of these risks, it is banned in the European Union and restricted in other regions. You are unlikely to find it in modern, well-formulated products.
Quick decision guide
Read the cautions before using
Bronidox can be useful, but watch for some irritation potential.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Bronidox.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
moderateCan bother some users, especially with frequent use, damaged skin, or strong companion ingredients.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A synthetic organic compound that acts as a broad-spectrum preservative, effective against bacteria, yeast, and mold. It belongs to the formaldehyde-releasing preservative family, meaning it slowly releases small amounts of formaldehyde to prevent microbial growth.
How it works
It works by slowly releasing formaldehyde over time, which kills or inhibits the growth of microorganisms. This helps keep the product safe from contamination during use.
Pros
Strong antimicrobial activity
Effective at low concentrations against bacteria, yeast, and mold, helping to keep products safe from contamination.
Cost-effective preservation
Inexpensive to produce and requires only small amounts to be effective, making it a budget-friendly option for manufacturers.
Cons and cautions
Skin irritation and allergy risk
Can cause contact dermatitis, especially in people with sensitive skin or those using products frequently.
Potential nitrosamine formation
May react with other ingredients to form nitrosamines, which are considered potential human carcinogens.
Regulatory restrictions
Banned in the European Union and restricted in other regions, limiting its use in modern cosmetics.
Best for
- Only in rinse-off products if absolutely necessary and at very low concentrations
- Formulators looking for a powerful preservative in regions where it is still allowed
Use caution if
- Anyone with sensitive or reactive skin
- Consumers seeking products free from formaldehyde-releasing preservatives
Usage tips
Safety summary
5-Bromo-5-nitro-1,3-dioxane is a controversial preservative due to its potential to cause skin irritation and form nitrosamines. It is banned in the EU and restricted elsewhere, making it a less desirable choice for modern formulations.
Research notes
Studies have shown that this ingredient can cause allergic contact dermatitis and that it releases formaldehyde, which is a known irritant. The potential for nitrosamine formation adds to safety concerns, leading to regulatory restrictions.
Common label clues
- Typical concentration
- Up to 0.1% in rinse-off products
- Regulatory status
- Banned in the European Union for use in cosmetics. Restricted in other regions, including the US, where it is allowed only in rinse-off products at concentrations up to 0.1%.
- Common uses
- Rinse-off products like shampoos and cleansers
- Environmental note
- Limited data on environmental impact, but as a synthetic halogenated compound, it may persist in water systems and affect aquatic life.
Good to know
- This ingredient is a formaldehyde-releaser, meaning it slowly releases small amounts of formaldehyde to preserve the product.
- It is often listed under the INCI name 5-BROMO-5-NITRO-1,3-DIOXANE on labels.
Common questions
What is Bronidox in beauty products?
5-Bromo-5-nitro-1,3-dioxane is a synthetic preservative that stops bacteria and fungi from growing in cosmetic products. It was once common in shampoos and body washes, but it has been linked to skin irritation and can form nitrosamines, which are potentially harmful compounds. Because of these risks, it is banned in the European Union and restricted in other regions. You are unlikely to find it in modern, well-formulated products.
What does Bronidox do in a beauty product?
It works by slowly releasing formaldehyde over time, which kills or inhibits the growth of microorganisms. This helps keep the product safe from contamination during use.
Is Bronidox safe for most people?
5-Bromo-5-nitro-1,3-dioxane is a controversial preservative due to its potential to cause skin irritation and form nitrosamines. It is banned in the EU and restricted elsewhere, making it a less desirable choice for modern formulations.
Who should be careful with Bronidox?
Anyone with sensitive or reactive skin Consumers seeking products free from formaldehyde-releasing preservatives
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.