Background: Fish allergy is a relatively common and potentially fatal condition. Most fish allergic subjects are allergic to multiple fish species. We encountered a patient clinically allergic only to swordfish.
Objective: To characterize the in vivo and in vitro IgE antibody responsiveness of this patient solely allergic to swordfish.
Methods: Prick skin tests, as well as immunoassay and protein immunoblotting for IgE antibody were performed using commercial fish extracts and fresh swordfish. A more typical multiple fish-allergic subject and a subject not allergic to food were also studied for comparison.
Results: The multiple fish-allergic subject demonstrated IgE antibody to a 13-kD protein in all fish tested (probably Gad c 1 and its analogues in other fish). The swordfish-allergic subject did not recognize this 13-kD band but did demonstrate IgE directed against a 25-kD band only in swordfish. The negative control showed no IgE binding to either the 13 or 25 kD bands.
Conclusions: It is possible to be allergic to a single fish species, such as swordfish, and such monospecific allergy may be due to the presence of species-specific allergens, in this case a 25-kD allergen in swordfish.