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An allergen is a substance that can cause an allergic reaction. In some people, the immune system recognizes allergens as foreign or dangerous. As a result, the immune system reacts by making a type of antibody called IgE to defend against the allergen. This reaction leads to allergy symptoms.


Common allergens include:

  • Animal proteins and animal dander
  • Dust
  • Drugs (such as antibiotics or medicines you put on your skin)
  • Foods (such as egg, peanut, milk, nuts, soy, fish, animal meat, and wheat)
  • Fungal spores
  • Insect and mite feces
  • Insect bites and stings (their venom)
  • Natural rubber latex
  • Pollen

Stewart GA, Richardson JP, Zhang J, Robinson C. The structure and function of allergens. In: Adkinson NF Jr., Bochner BS, Burks AW, et al., eds. In: Middleton's Allergy Principles and Practice. 8th ed. Philadelphia, PA: Elsevier Mosby; 2014:chap 26.

Review Date: 2/15/2015
Reviewed By: Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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