Abstract Rationale Sweet potato is a member of the convolvulaceae family, genus Ipomoea Batatas . In spite of being widely harvested for feeding, there are not published allergic reactions to it. Methods We report three cases of allergy to sweet potato. Only one of these patients was atopic. Patient number 1 suffered from generalized urticaria with hypotension and edema in hands and face immediately after eating a roasted sweet potato. Patient number 2 presented urticaria, nausea, vomiting, dizziness and lost of consciousness thirty minutes after eating a baked sweet potato. Patient number 3 had edema in hands and face as well as sensation of tickling in the throat and tightness several hours after ingesting a sweet potato. Skins tests (prick-prick and prick with an extract obtained from our laboratory), ELISA IgE, and Immunoblot were performed in all patients. Results All skin tests were negative; However serum specific IgE (s IgE) was detected by ELISA and/or Immunoblot in the three of them. The allergenic bands found in patient number three were of 54–64 kD and in patient number 3 were of 19–24 and 74 kD. Likewise, skin tests and s IgE to several other foods were negative. Conclusions We report three cases of anaphylaxis in adult patients, caused by sweet potato; the diagnosis was suggested by clinical history and in vitro tests. We have not found any other case of allergy caused by Ipomoea Batatas in literature.