Some cosmetics chemicals are designed to react with water in the bottle to generate a little formaldehyde, a preservative, to keep the product from growing mould and bacteria.
But formaldehyde is a potent allergen which the World Health Organization consider carcinogenic.
Formaldehyde releasers include DMDM hydantoin, imidazolidinyl urea, diazolidinyl urea, and quaternium-15.
A 2010 study found that nearly one fifth of cosmetic products contained a formaldehyde releaser. Johnson & Johnson, a personal care products giant, is phasing out formaldehyde releasers under pressure from health advocates
Where do you find them?
Shampoos, conditioners, bubble bath and other personal care products.