A type I allergic reaction; so called because in a sensitised subject the reaction becomes evident usually within minutes after contact with the allergen (antigen), reaches its peak within an hour or so, then rapidly recedes. ... See: immediate reaction, anaphylaxis. ... Compare: delayed allergy. ... (05 Mar 2000) ... 
Type: Term Synonyms: immediate hypersensitivity
[n] - an allergic reaction that becomes apparent in a sensitized person only minutes after contact