Food additives can induce a wide range of adverse reactions in sensitive individuals. A prevalence of 0.03% to 0.23% is estimated. The complexity of the different pathophysiologic mechanisms possibly involved in the allergic (immunologic) or in the intolerant (nonimmunologic) reactions to food additives continues to create great difficulties in the understanding of such conditions. From the clinical point of view it is useful to make a distinction between an intolerance reaction and intolerance provocation. The pathogenic mechanisms of adverse reactions to the azo dye tartrazine and to sulfite preservatives are discussed briefly. Due to the lack of reliable skin or in vitro tests, the diagnosis of an intolerance to food additives is still based on placebo-controlled oral provocation tests. Two typical cases of a "restaurant syndrome" due to sulfite allergy or sensitivity are described, as well as a case of disulfite-induced urticaria-vasculitis and a case of anaphylactoid purpura associated with tartrazine and benzoates.