Buckwheat, which has been abundantly consumed in Asian countries and has been increasingly popular in the United States, Canada, and Europe, can be a potent allergen when ingested or inhaled. A case is reported of a 36-year-old man who experienced nausea, vomiting, urticaria, a sensation of throat closing, inability to speak, dyspnea, and dizziness shortly after ingesting a large portion of buckwheat that required emergency room treatment. In the previous 2 years he had experienced asthma, contact urticaria, allergic conjunctivitis, and allergic rhinitis from sleeping with a buckwheat pillow. Six months after the first ingestion reaction, the patient again experienced anaphylaxis requiring emergency treatment when he accidentally ate crackers with a small amount of buckwheat. Skin-prick testing showed a strong positive response to buckwheat, and a radioallergosorbent assay test was highly positive to buckwheat. It is possible that inhaled buckwheat provoking asthma sensitized the patient before his two episodes of ingestion anaphylaxis. Buckwheat is a potent allergen that can induce various clinical manifestations in the same individual.