The existence of the canine hookworm Ancylostoma caninum in the human
gut stems to be curtailed by an effective IgE-mediated inflammatory re
sponse against the helminth's feeding secretions, which, by damaging t
he host, compromises the parasite's feeding opportunities. In contrast
, immunity does not develop against adapted, anthropophilic hookworm s
pecies, and it is suggested this relates to modulation of the inflamma
tory response by hookworm secretions. Here, John Croese discusses this
hypothesis and its implications for the development of drugs to suppr
ess allergy.