The development of biotechnology for the production and processing of foods raises the question of the safety of these foods and the evaluation of any risks, including the allergic risk, that their consumption could pose to Public Health.Indeed allergies engendered by foods containing or derived from genetically modified organisms (GMOs) is a special issue on which particular emphasis has been placed. European Union's regulation 258/97 on Novel Foods stipulates that it must be addressed in every application for the authorization to put on the market any novel foods and particularly those containing or derived from GMOs. Assessment of the allergic risk is  currently performed using the decision tree approach as described in the ILSI-IFBC recommendations. The aim of this paper is to analyse for the different steps of this approach whether human studies may be necessary to assess the allergic risk of long term or high dosages consumption of such novel foods and how post market surveillance could provide such informations in addition of a priori (e.g. pre-marketing) safety evaluation by testing methodologies currently used as yet.