Ma'anar ƙamus na "allergic reaction" amsa ce ta ilimin lissafi ga wani abu wanda yawanci ba shi da lahani, amma wanda jiki ya gane a matsayin barazana. Wannan martani yana haifar da tsarin rigakafi, wanda ke samar da ƙwayoyin rigakafi don yaƙar barazanar da ake gani. Alamomin rashin lafiyan na iya kamawa daga m, kamar atishawa da ƙaiƙayi, zuwa mai tsanani, kamar anaphylaxis, wanda zai iya zama barazanar rai. Allergens na yau da kullun sun haɗa da pollen, ƙura, mold, dander, wasu abinci, da magunguna.