We recently experienced a 29-year-old female with anaphylaxis caused by linseed included in homemade bread. This is the first report of linseed-induced allergy in Japan. She obtained the linseed-containing ingredients of bread by mail order. We performed skin-prick tests and basophil degranulation tests using extracts of the ingredients and commercially available linseeds; both tests showed positive results for linseed. The patient's serum was also positive for linseed-specific IgE. Since linseeds are included in various kinds of foods and exposure to them is increasing, linseeds may need to be recognized as a potential trigger of immediate-type allergy in Japan.