Allergen

An allergen is a substance that triggers an allergic immune response in a susceptible person. Common allergens include proteins in pollen, foods, animal dander, and insect venom.

Immunoglobulin E: An antibody class that binds allergens and helps trigger immediate allergic reactions. IgE binds many allergens and arms mast cells for rapid responses.
Allergy testing: Medical tests that assess whether a person is sensitized to particular allergens. Testing can identify candidate allergens, interpreted alongside a person's symptoms.
Allergy: An immune response to an ordinarily harmless substance that causes symptoms or tissue injury. An allergen is the trigger within the broader phenomenon of allergy.
Pollen: Fine particles released by plants for reproduction, some of which trigger seasonal allergies. Airborne pollen is a common cause of allergic rhinitis.
Irritant: A substance that directly damages or inflames tissue without requiring an allergen-specific immune response. Irritants can mimic allergy symptoms without allergen-specific sensitization.
Mast cell: A tissue immune cell that releases histamine and other mediators during allergic reactions. Allergen-cross-linked IgE on mast cells prompts mediator release.
Skin prick test: A diagnostic test that introduces small amounts of suspected allergens into the skin to look for a local reaction. This common test checks for immediate skin responses to selected allergens.
Antigen: A molecule or molecular structure recognized by antibodies or immune-cell receptors. Allergens are antigens that provoke allergic responses in susceptible people.
Peanut allergy: An immune-mediated allergy to peanut proteins that can cause reactions ranging from hives to anaphylaxis. Peanut proteins are food allergens associated with potentially severe reactions.
Pseudoallergic reaction: A reaction resembling allergy that occurs without the usual allergen-specific IgE mechanism. Similar symptoms can arise through pathways that do not involve an allergen-specific response.

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