Alternative names
Allergy-causing; Allergen

An allergen is a substance that can cause an allergic reaction. Allergens are substances that, in some people, the immune system recognizes as “foreign” or “dangerous” but cause no response for most people.


Common allergens include:

  • chemicals and plants  
  • drugs (such as antibiotics, serums)  
  • foods (such as milk, chocolate, strawberries, wheat)  
  • infectious bacteria, viruses, and animal parasites  
  • inhalants (such as dust, pollen, perfumes, smoke)  
  • physical agents (such as heat, light, friction, radiation)

See also:

Johns Hopkins patient information

Last revised: December 3, 2012
by Martin A. Harms, M.D.

Medical Encyclopedia

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