Molecular allergology is a breakthrough science that enables the quantification of IgE and IgG antibodies against individual allergen protein components at a molecular level. The diagnosis of IgE-mediated allergic disorder among children is based on clinical history and sensitization demonstrated through an allergy test. Identifying whether the sensitization is primary (species specific) or a result of cross-reactivity to proteins with similar protein structures helps the clinician to judge the risk of allergic reaction. This is possible today because allergen component tests are now available for clinicians to use in everyday practice. This article focuses on clinical utility through the prediction of cross-reactivity or primary sensitization, estimation of the risk of reaction to heated food and the risk of severe clinical symptoms.