Background: Oral allergy syndrome (OAS) is the mildest form of an allergic reaction to foods. It is characterized by the presence of IgE mediated symptoms restricted to oral mucosa after intake of fresh fruits and vegetables. OAS diagnosis is based on suggestive clinical manifestations and can be con rmed with tests such as prick-to-prick skin test with the food implicated, which have a sensitivity > 90%, speci city 30-60%, positive predictive value (PPV) of 40% and negative predictive value (NPV) > 95%. Objective: To know the prevalence of OAS in adult patients attending a third level hospital in southern Mexico City, and also describe the demographics of these patients and comorbidities more frequently associated. Patients and method: We studied 44 patients (40 women and 4 men), with an average age of 33.4 years, with suggestive clinical features of OAS, evaluated with prick-by-prick skin tests with fresh food. Results: There was a predominance of OAS in woman (91%) and a prevalence of asthma and allergic rhinitis of 54% among this population. We found that 60.4% of these patients had positive prick-by-prick skin tests, being the most frequently involved families of foods: rosaceae (60%), crustaceans (25%), musaceae (23%), actinidacea (21%), laura- ceae (16%) and cucurbitaceae (16%). Only 5 patients presented adverse reactions with prick-by-prick skin tests, in 4 of the cases with grade 3 and grade 4 anaphylaxis, while testing with banana-watermelon, peach, papaya and peanut, respectively. Conclusions: Oral allegy syndrome affects more women than men, the most frequent comorbidities in patients with oral allergy syndrome are allergic rhinitis and asthma, thus, in patients with asthma and allergic rhinitis, sensitized to pollens we have to ask about symptoms suggestive of oral allergy syndrome.