In safety assessment of novel foods such as functional foods, allergy is a special issue on which particular emphasis has been placed. The reason for such concern is that incidence of food allergies is constantly and rapidly increasing. The severity of the reported incidents and the number of foods incriminated are also on the rise. The outstanding challenge is to understand what makes a common innocuous protein or peptide behave as an allergen for some groups of people, or why it may suddenly or progressively become a much more potent allergen than usual. It is therefore necessary to consider the risks of creating or unmasking new immunoreactive structures, or of overexposure to already reactive substances, as a result of new food-production and processing technologies. No test such as the use of animal models, the analysis of structure, function and physico-chemical properties is as yet available to evaluate or predict the allergenicity of a 'novel' protein in a wholly reliable and objective manner. No indication has yet suggested that novel foods, and particularly recombinant proteins or genetically modified foods, would be more (or less) allergenic than the corresponding conventional foods. No particular structure can be described as being solely and intrinsically allergenic. The predictive approaches to determining the allergenic potential of NFs should therefore be subject to case-by-case critical appraisal allied to mandatory implementation of monitoring of the potential postmarketing impact of these new foodstuffs on public health