Allergies & immunity

An allergy is your immune system reacting to something harmless as though it were dangerous. This section covers hay fever, food and drug allergies, eczema, hives, asthma triggers, and the autoimmune conditions where the immune system turns on the body itself. You will find what causes each one, how allergists test for them, and what works, from avoidance to antihistamines to immunotherapy. Most allergies are an inconvenience. A few are not: call 911 for trouble breathing, swelling of the face or throat, or sudden collapse after a sting, a food, or a medication.