Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
An allergen is a typically harmless substance that triggers an exaggerated immune response, known as hypersensitivity, in susceptible individuals. Common allergens include pollen, dust mites, pet dander, and certain foods.
5 Must Know Facts For Your Next Test
Allergens can trigger various types of hypersensitivities, most commonly Type I (immediate) hypersensitivity.
Exposure to allergens leads to the production of IgE antibodies by B cells.
Mast cells and basophils play a crucial role in allergic responses by releasing histamines upon activation by IgE-allergen complexes.
Symptoms of allergic reactions can range from mild (e.g., hay fever) to severe (e.g., anaphylaxis).
Genetic predisposition and environmental factors both contribute to the likelihood of developing allergies.