allergy
n. countablen. a medical condition that makes you feel sick or get a skin rash when you eat, touch, or breathe something. Common things that cause this are peanuts, pollen, or cat hair.
n. an immune system overreaction to a typically harmless substance, such as pollen, food, or animal dander. Often used with the preposition 'to' when specifying the trigger.
I have a severe allergy to peanuts.
Spring is a difficult season for people with a pollen allergy because the high counts cause constant sneezing.
While some reactions are merely irritating, a systemic allergy can lead to anaphylaxis, requiring immediate medical intervention to prevent respiratory failure.
Borrowed from German Allergie. Coined by Austrian pediatrician Clemens von Pirquet in 1906 from Ancient Greek ἄλλος (állos, “other”) + ἔργον (érgon, “work, activity”), on the model of Energie.
Commonly takes the preposition 'to' before the allergen.
I have allergy of catsI have an allergy to catsAllergy requires an article ('an') and takes the preposition 'to' rather than 'of'.