Adverse hypersensitivity reactions to natural foods and certain drugs and food additives are mediated by immunological (allergy) or non-immunological mechanisms. Some clinical and physiological similarities have been noted between these allergic and non-allergic reactions. This observation has led to the concept of "pseudoallergic reactions-PAR". PAR can be triggered in various ways such as: interactions with the central or peripherical nervous system, non-specific release of mediators, enzyme inhibition due to hereditary or pharmacologically induced enzyme deficiencies and pharmacological properties of some natural food constituents such as biogenic amines. The prevalence of adverse reactions to food additives has been calculated to be about 0.1%. PAR to food additives occurs frequently in patients suffering from urticaria, asthma and may be accompanied by history of aspirin or NSAI pseudoallergic reactions. The same additives (azo dyes, sulphites, benzoates) are used in various drug formulations and may be responsible for eliciting PAR. In Poland, labelling of food additives, following the "E number system", has been mandatory since 1993. Unfortunately, this satisfactory trend has not yet been applied to drug additives. The diagnosis of PAR to food additives is based on the anamnesis with analysis of the patient's drug and dietary intake. Skin tests and "in vitro" tests are only sporadically informative. In each individual patient, a specific challenge with additives is desirable. Food additives may be tested according to the schedule based on DBPCFC principle. Individually performed exclusion regimes are the principal methods of prevention.