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 immunoglobulin E (IgE) to defend against the allergen. This reaction leads to allergy symptoms.
Common allergens include:
- Animal proteins and animal dander
- 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 latex rubber
Stewart GA, Robinson C. The structure and function of allergens. In: Burks AW, Holgate ST, O'Hehir RE, et al, eds. Middleton's Allergy: Principles and Practice. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 26.
Review Date 2/2/2023
Updated by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.