From an immunological perspective, an allergy is a form of hypersensitivity. It's an immunological dysfunction in which bodily tissues overreact to normally harmless substances, launching an all-out assault on things like pollen and dust mites that come in contact with the body. This triggers various defensive reactions (e.g. inflammation), but also, when serious, destroys bodily tissues along with the harmless foreign substances.
從免疫學來說，「過敏」名副其實，是一種身體組織對外在無害物質過於大驚小怪的免疫失調疾病，例如對接觸身體的花粉、塵●大舉發動免疫攻擊，不僅引發各種作戰反應（發炎），嚴重時還會和這些完全無害的外來物「玉石俱焚」。