This review on in-vitro diagnostic methods focuses on the use of methods to perform risk assessment on foods. Based on the International Life Science Institute (ILSI) risk decision tree, the methods are discussed and three scenarios are suggested: (i) testing for a well-known allergen; (ii) testing for a well-known allergen, but with no previous history of food allergy; and (iii) testing for unknown allergens and cross-reactivity with known allergens.