Bronopol, a common preservative, causes skin irritation through multiple mechanisms—not just from the formaldehyde it releases. When bronopol breaks down in your skin, it creates other reactive compounds (like 2-bromoethanol) that trigger immune responses at much lower doses than formaldehyde alone would. This means some people might react to bronopol even if they're not sensitive to formaldehyde.

Researchers tested bronopol and formaldehyde in labs using chemical analysis and human immune cells to see how each one reacts with skin proteins and activates immune responses. They compared the two side-by-side to identify which compound was actually causing the irritation.

Funding not disclosed in abstract