Researchers found formaldehyde in 18% of cosmetic products that didn't list any formaldehyde-releasing preservatives on their ingredient labels. The hidden formaldehyde averaged 105 ppm (ranging from 0.5-507 ppm), with self-tanners potentially contaminated through impurities in the tanning ingredient dihydroxyacetone. This matters because formaldehyde is a common contact allergen that can trigger skin reactions even when you don't know it's in your product.

Scientists tested 142 leave-on cosmetics (mostly creams) for formaldehyde using two detection methods: a screening test on all products, then a more detailed analysis on those that tested positive. They also tested raw materials and packaging to understand where the hidden formaldehyde was coming from.

Funding not disclosed in abstract