Oral allergy syndrome (OAS) is one of the most common types of food allergy. The syndrome includes itching and swelling of the lips, palate and tongue, usually after consuming fresh fruits and vegetables. The underlying pathogenic mechanism is cross-reactivity between IgE antibodies specific to pollen, and antigens in food, such as fresh fruits, vegetables and nuts that are structurally similar to pollen. Both pollen and food antigens can bind to IgE and trigger type I immune reaction. Diagnosis is primarily based on the patient's history, and confirmed by skin tests, in vitro tests, and oral provocation tests. Differential diagnoses include many diseases (such as burning mouth syndrome, angioedema, hay fever, various other oral diseases, etc.), and for this reason a multidisciplinary approach is necessary, as different specialists need to be involved in the diagnostic procedure. Therapy includes avoiding, or thermal processing of, fruit and vegetables known to trigger a reaction, and antihistamine medications. If a more severe anaphylactic reaction develops, more aggressive therapy is required. The goal of this article is to present OAS, its etiopathogenesis, clinical picture, and symptoms, diagnostic approach and therapy for OAS.