IGHE and mastocytosis: The symptoms experienced during an adverse reaction can vary between individuals depending on a multitude of factors: (i) some are related to the host, for example, the age (teen age and adult youth represent a risk factor for fatal reactions), allergic comorbidities (e.g., asthma and mastocytosis), and previous adverse reactions; (ii) some are related to the allergen (e.g., dose of allergen and food processing); (iii) some are related to the IgE-mediated immune response (e.g., IgE level); and (iv) others are probably unknown [145].