allergy

American  

[al-er-jee] / ˈæl ər dʒi /

noun

allergies plural

1. an abnormal reaction of the body to a previously encountered allergen introduced by inhalation, ingestion, injection, or skin contact, often manifested by itchy eyes, runny nose, wheezing, skin rash, or diarrhea.

2. hypersensitivity to the reintroduction of an allergen.

3. Informal. a strong dislike or aversion, as toward a person or activity.

   He has an allergy to hard work.

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allergy British  

/ ˈælədʒɪ /

noun

1. a hypersensitivity to a substance that causes the body to react to any contact with that substance. Hay fever is an allergic reaction to pollen

2. informal aversion

   he has an allergy to studying

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allergy Scientific  

/ ăl′ər-jē /

1. An abnormally high immunologic sensitivity to certain stimuli such as drugs, foods, environmental irritants, microorganisms, or physical conditions, such as temperature extremes. These stimuli act as antigens, provoking an immunological response involving the release of inflammatory substances, such as histamine, in the body. Allergies may be innate or acquired in genetically predisposed individuals. Common symptoms include sneezing, itching, and skin rashes, though in some individuals symptoms can be severe.

2. See also anaphylactic shock

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allergy Cultural  

1. A highly sensitive reaction of the body to certain substances, such as pollen, that are present in amounts that do not affect most people. Common indications of allergy include sneezing, skin rashes, itching, and runny nose.

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Other Word Forms

Noun Inflected Forms

• allergies
  plural

Etymology

Origin of allergy

1910–15; < Greek áll ( os ) other + -ergy < Greek -ergia, equivalent to érg ( on ) activity + -ia -y ³

Explanation

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."

Example Sentences

David Morens, 78 years old, of Chester, Md., served as a senior official at the National Institute of Allergy and Infectious Diseases, or NIAID, between 2006 and 2022.

From The Wall Street Journal • Apr. 28, 2026

Allergy expert Professor Stephen Till, from Guy's and St Thomas' Hospitals in London, recommends "a cocktail approach", which means taking:

From BBC • Apr. 22, 2026

That would include major cuts to the National Institute of Allergy and Infectious Diseases, which was formerly headed by the respected immunologist Anthony Fauci.

From Los Angeles Times • Apr. 7, 2026

His mother Helen, who has campaigned alongside the National Allergy Strategy Group, describes today's announcement as "a really significant day".

From BBC • Mar. 5, 2026

I think we finally just gave up and watched America’s Unlikeliest Allergy Attacks.

From "Feed" by M.T. Anderson

Related Words

• hay fever