allergy

/ˈælərdʒi/

/ˈælədʒi/

Other forms: allergies

An allergy is a physical reaction to some specific food or substance. If you have an allergy to cats, they'll make you itchy and swollen no matter how much you love to pet them.

If you have an allergy, it can range from mild — itchy eyes in the springtime — to serious — being unable to breathe after eating a peanut. People have allergies to all kinds of things, including milk, chocolate, corn, dust, mold, and just about any kind of animal you can think of. Allergy was originally Allergie, a German word invented by a doctor who combined the Greek roots allos, "other, different, or strange," and ergon, "activity."

Definitions of allergy

1. noun

   hypersensitivity reaction to a particular allergen; symptoms can vary greatly in intensity
   synonyms: allergic reaction

   types:

   food allergy

   allergic reaction to a substance ingested in food

   atopic allergy, atopy, immediate allergy, type I allergic reaction

   an allergic reaction that becomes apparent in a sensitized person only minutes after contact

   serum disease, serum sickness

   a delayed allergic reaction to the injection of an antiserum caused by an antibody reaction to an antigen in the donor serum

   delayed allergy, type IV allergic reaction

   an allergic reaction that becomes apparent only hours after contact

   type of:

   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