Tartrazine (FD & C Yellow No. 5) is an approved azo dye present in many drugs and food products. During the 1970s, many cases of tartrazine sensitivity were reported. This led to new regulations that required the listing of azo dyes on package inserts of drugs and on packages of food products. Tartrazine sensitivity is most frequently manifested by urticaria and asthma. Although azo dyes have been implicated in accentuating hyperkinetic syndromes, tartrazine is not considered an offender. Vasculitis, purpura and contact dermatitis infrequently occur as manifestations of tartrazine sensitivity. Cross-sensitivity in aspirin-sensitive and NSAID-sensitive patients may also occur. The mechanism of sensitivity is obscure and has been called pseudoallergic. Management consists mainly of avoidance of drugs and food products that contain tartrazine.