Water caltrop flour (also known as water chestnut) is a commonly consumed Asian food. There are no data on the prevalence of IgE-mediated hypersensitivity reactions to water caltrop but it is believed to be very rare.
A 57-year-old gentleman of an Asian background developed generalised urticaria, breathlessness and loss of consciousness following ingestion of Singoda flour (water caltrop flour). He was successfully resuscitated with adrenaline, chlorpheniramine and hydrocortisone. Acute mast cell tryptase was elevated and the skin prick test to water caltrop seed was positive. Symptomatology, temporal association, elevated acute serum tryptase and a positive skin test were in keeping with a type 1 hypersensitivity reaction to water caltrop.
To the best of our knowledge, this is the first published case report on water caltrop-induced anaphylaxis. Further studies are needed to characterise the allergenic components in water caltrop and to identify possible cross-reactivities.