Allergy Meaning: When the Body Attacks Something Harmless
An allergy is a reaction in which the immune system treats a harmless substance as a threat, producing symptoms from a runny nose to a life-threatening collapse.
An allergy is an immune response to something that is not actually dangerous — pollen, peanuts, cat dander, penicillin. The substance is called an *allergen*, and the reaction ranges from mildly annoying to fatal.
- An immune reaction. *She has an allergy to shellfish.*
- A strong dislike (informal). *He has an allergy to paperwork.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | allergy | A nut allergy. |
| Plural | allergies | Seasonal allergies. |
| Adjective | allergic | She is allergic to bees. |
| Noun | allergen | Dust mites are a common allergen. |
| Person | allergist | Referred to an allergist. |
How it is used in a sentence
- Tell the kitchen about any allergies before ordering.Standard restaurant phrasing.
- He is allergic to penicillin.Allergic to, always with to.
- Hay fever is an allergy to pollen.A common everyday example.
- She seems to have an allergy to being told what to do.The informal, joking use.
Allergy, intolerance and sensitivity
- Allergy — the immune system is involved; reactions can be severe and fast
- Intolerance — digestion is involved, as with lactose; unpleasant but not immune-driven
- Sensitivity — a loose term for reacting to something at lower doses than most people
Coined in 1906 by the Austrian paediatrician Clemens von Pirquet, from Greek *allos* (other) and *ergon* (work) — literally an altered reaction.
What is anaphylaxis?
A severe, rapid allergic reaction affecting the whole body. It is a medical emergency and is treated with adrenaline.
Can you develop an allergy as an adult?
Yes. Allergies can appear at any age, and childhood allergies sometimes fade.