The immune system sometimes mistakes harmless substances for threats. An allergy is an exaggerated immune response to a normally innocuous environmental antigen such as pollen, food protein, or medication.

IgE antibodies and mast cells drive the classic immediate reactions: sneezing, itching, hives, wheezing, or anaphylaxis. Delayed reactions involve other immune pathways and can produce eczema or contact dermatitis. Diagnosis rests on history, skin testing, and sometimes blood tests for specific IgE. Avoidance remains the primary management step; antihistamines, corticosteroids, and epinephrine treat symptoms or emergencies.

Allergies are common and range from seasonal nuisance to life-threatening emergency. Patients who have experienced anaphylaxis must carry epinephrine and understand trigger avoidance. Desensitization protocols exist for selected allergens when avoidance is impractical.

• Exaggerated immune response to a harmless substance
• Mediated largely by IgE and mast-cell activation
• Symptoms range from mild to anaphylactic
• Managed by avoidance, medication, and sometimes desensitization