In food allergy, only a restricted number of protein families have been identified to contain allergenic proteins. These can be further grouped into major allergens, responsible for inducing allergic reactions in the majority of patients allergic to the food source, as compared to minor allergens only affecting a small number of food allergic patients. In addition, rare allergens have only been described for single cases so far. Rare allergens can derive from novel foods, including exotic varieties and foods not yet frequently consumed in certain regions. Also, new or modified processing strategies could induce a higher allergenicity in certain dietary proteins. And finally, low abundancy and/or low allergenic activity may also account for some rare allergens. For allergenic risk assessment, cross-reactivity of novel allergens with already known allergens is in place and facilitates the identification of potential new allergens, while de novo sensitization to yet undefined allergens can only be described retrospectively. This review presents some examples of recently identified rare allergens.