According to modern concepts, food ¬allergy is usually divided into two classes or types. The first includes allergic reactions to stable (complete) food allergens. These allergens are resistant to high temperatures, pH changes and proteases.Oral allergy syndrome (OAS) is defined as a set of clinical manifestations caused by IgE -mediated allergic reactions that occur at oral and pharyngeal mucosae in the patients with pollen sensitization after ingestion of certain fruits, vegetables, nuts and spices.