Tartrazine (FD&C Yellow No. 5) and other allowed certified color additives may have an exacerbating effect in chronic urticaria and asthma sufferers. In the individual patient the only way to determine their relevance is to administer test doses. By altering doses, timing and substances and by interspacing controls a battery of tests has been developed. Methods of testing for sensitization to food additives and analgesics are described.