A clinical case of anaphylaxis after eating oatmeal contaminated with booklice (Liposcelis bostrychophila)

A 52-year-old man presented to our department with generalized erythema, watery stools, and vomiting 30 min after ingesting coconut, oatmeal, and vegetable juice. On arrival, his blood pressure was 120/79 mm Hg, heart rate was 126 beats per min, blood oxygen saturation was 96%, and lip cyanosis was observed. The patient experienced diffuse redness throughout the body and was diagnosed as having severe anaphylaxis. A skin prick test for the leftover coconut, oatmeal, and vegetable juice, which the patient had consumed immediately before the onset of symptoms, showed a positive reaction only to the leftover oatmeal. Direct microscopic examination of the leftover oatmeal revealed numerous insect bodies that appeared as booklice. Using Western blot analysis and quantitative polymerase chain reaction, Lip b 1, a specific antigen for Liposcelis bostrychophila (badonnel), an indoor pest that inhabits various places and feeds on various indoor materials, including stored foods, was detected only in the extract of the leftover oatmeal. Based on these results, we identified an insect body infesting oatmeal, L. bostrychophila. The serum level of L. bostrychophila-specific immunoglobulin antibodies was higher than the cutoff value; therefore, we identified the disease as anaphylaxis caused by accidental ingestion of L. bostrychophila that infested the oatmeal stored in the container. We report the first case of L. bostrychophila-infested oatmeal as an orally ingested allergen in Japan.