WOMEN who wear nail varnish should choose one containing polyester resin rather than the more common type based on formaldehyde, say researchers from Sweden. A study, published in the British Journal of Dermatology, showed that most nail varnish can cause allergy on the eyelids, face, neck and hands. Some women in the study had to be hospitalised. Cosmetics manufacturers should be required to label products with their ingredients to help people with allergies, the researchers argue.