A method for treating chemo therapy or radiation therapy side effects in a mammal undergoing chemotherapy and/or radiation therapy, the method comprising a step of administering to the mammal a therapeutically effective amount of a RAR antagonist or RAR inverse agonist which binds to receptors of the RAR&alpha；, RAR&bgr； and RAR&gamma； subtypes is disclosed. Such side effects include chemoradiotherapy-induced alopecia, chemoradiotherapy-induced thrombocytopenia, chemoradiotherapy-induced leucopenia and chemoradiotherapy-induced neutropenia.
