Allergens

Allergens are substances capable of triggering an allergic reaction in people who are sensitized to them. In sensitized individuals, exposure to an allergen can cause the immune system to produce specific IgE antibodies. Upon subsequent exposure, the allergen binds to IgE on mast cells and basophils, releasing mediators such as histamine and leading to symptoms that can range from mild to life-threatening.

Common allergen sources fall into several categories. Food allergens include milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, and soy. Inhalant allergens include pollen from trees, grasses, and weeds; mold spores; dust mites; and animal dander. Other significant allergens are insect venoms, certain medications, latex, and occupational chemicals. Some people have allergies to multiple substances.

Diagnosis typically relies on a careful history and confirmation with tests. Skin prick testing or serum-specific IgE testing can indicate sensitization, but a positive test does not always correlate with clinical symptoms. In some cases an oral food challenge or controlled exposure under supervision is used to establish clinically relevant food allergies.

Management emphasizes avoidance of known allergens, environmental controls, and patient education. For those at risk of anaphylaxis, an epinephrine auto-injector and an individualized emergency action plan are essential. Medications such as antihistamines, intranasal or inhaled corticosteroids, and, when appropriate, bronchodilators may relieve symptoms. Allergen immunotherapy (shots or sublingual tablets) is available for certain aeroallergens and venom allergies and can reduce symptoms for some patients.

Cross-reactivity between related allergens can complicate diagnosis and management. Public health measures often include labeling and guidance to help individuals avoid hidden allergens in foods and products.