allergier

Allergies, or allergier, are a group of immune-related conditions characterized by an overreaction to otherwise harmless substances called allergens. In sensitized individuals, exposure to an allergen triggers the production of specific IgE antibodies. On subsequent exposures, these antibodies recognize the allergen and release chemical mediators such as histamine from mast cells, causing symptoms in the respiratory tract, skin, eyes, gastrointestinal tract, or circulatory system in severe cases.

Common types of allergic reactions include allergic rhinitis (hay fever) with sneezing, nasal congestion, and itchy eyes; allergic conjunctivitis affecting the eyes; allergic asthma with wheeze and shortness of breath; atopic dermatitis (eczema) presenting as itchy, inflamed skin; and food allergies that can cause a range of symptoms from hives to anaphylaxis. Insect venom allergies are another important category, and contact dermatitis results from skin contact with certain substances.

Diagnosis relies on a careful medical history, identification of patterns with exposures, and confirmatory tests such as skin prick tests or serum-specific IgE measurements. In some cases, supervised oral food challenges or targeted tests for venom or drug allergies are used.

Management focuses on avoidance of known triggers when possible, and treatment tailored to the condition. Pharmacologic options include antihistamines, intranasal or inhaled corticosteroids, leukotriene receptor antagonists, bronchodilators, and, in severe reactions, epinephrine for anaphylaxis. Allergen immunotherapy (subcutaneous or sublingual) can modify the immune response for some allergies. Patient education on recognition of early symptoms and action plans is essential, particularly for those at risk of anaphylaxis.

Epidemiologically, allergies are common worldwide, with prevalence varying by region and age. They can have a significant impact on quality of life and, in some cases, require lifelong management.