<Tr> <Th> MeSH </Th> <Td> D006969 </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> Type I hypersensitivity (or immediate hypersensitivity) is an allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen . Type I is not to be confused with type II, type III, or type IV hypersensitivities, nor is it to be confused with Type I Diabetes or Type I of any other disease or reaction . </P> <P> Exposure may be by ingestion, inhalation, injection, or direct contact . </P>

Type of antigen that triggers an allergic reaction