- hypersensitivity reaction - an inappropriate and excessive reaction to an allergen (as pollen or dust or animal hair or certain foods); severity ranges from mild allergy to severe systemic reactions leading to anaphylactic shock
--1 is a kind of hypersensitivity
--1 has particulars:urtication, urticaria, hives, nettle rash; allergy, allergic reaction; anaphylaxis; allergic rhinitis