Anaphylaxis after eating mite-infested wheat flour has been recently reported. This paper is to describe two cases and examine the occurrence of mite contamination in wheat flour in Japan. Packages of wheat flour from retail outlets and homes were examined microscopically for the presence of mites. Three of 176 packages from retail outlets and seven of 127 from homes were infested with mites, and it seems likely that the mite contamination takes place in most cases at homes after the packages have been opened. No mites were found in packages stored in a refrigerator, therefore, mite-sensitive patients must be advised to store wheat flour products in a refrigerator.