An allergen is a substance that can cause an allergic reaction. In some people, the immune system thinks allergens are foreign or dangerous. This is what leads to allergy symptoms.
Common allergens include:
Wasserman SI. Approach to the patient with allergic or immunologic disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 257.
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