Up to 78 percent of relaxers, which are used to permanently straighten hair, contain hormone-disrupting chemicals, known as parabens, a US study found.
Past studies suggest parabens, which are used as preservatives, mimic oestrogen and may cause cancer, weight gain and reduced muscle mass.
Up to 78 percent of hair products, including leave-in conditioners, also contain phthalates, the research adds.
Phthalates are added to prolong products’ shelf lives and have been linked to breast and ovarian cancer, as well as early menopause.
Out of the 18 products analysed, 11 contain chemicals that are banned under the EU cosmetic regulations due to their links to cancer and female infertility.