n. any one of a group of drugs derived from vitamin A. They bind to one or more of six specific receptors that are found on many cells. On the skin they act to cause drying and peeling and a reduction in oil (sebum) production. These effects can be useful in the treatment of severe *acne, *psoriasis, *ichthyosis, and other skin disorders. Retinoids include *isotretinoin, *tretinoin, acitretin, tazarotene, and alitretinoin, which is particularly effective for hyperkeratotic hand eczema. Possible side-effects, which may be serious, include severe fetal abnormalities (if taken by pregnant women), toxic effects on babies (if taken by breastfeeding mothers), liver and kidney damage, excessive drying, redness and itching of the skin, and muscle pain and stiffness.