An allergy is an immune system reaction to an outside (foreign) substance that does not usually cause a reaction in most people. Your immune system creates antibodies, which are substances that protect you from outside invaders that could make you sick. When you have allergies, your immune system makes antibodies for a particular substance because it considers the substance harmful to the body, even though it is not. Your immune system then keeps these antibodies so that, if you are ever exposed to the substance again, your immune system can react. This reaction can cause redness and swelling (inflammation) of your skin, sinuses, airways, or digestive system. The severity of allergies is different from person to person. The most common allergies include hay fever (pollen), food (peanuts), insect stings (bee stings), and drug allergies (antibiotics).
Allergy symptoms vary based on the substance involved and can involve the airways, sinuses, skin, and digestive system (stomach and intestines). Mild allergy symptoms include sneezing, itching and a skin rash while the most severe reaction, known as anaphylaxis, can cause unconsciousness, shortness of breath, decreased blood pressure and a weak pulse. Allergy risk factors include having a family history of asthma or allergies, being a child, and having asthma or another allergic condition. To diagnose allergies, your doctor may ask detailed questions about signs and symptoms and ask you to keep a detailed diary of symptoms and possible triggers. Your doctor may also perform a skin test, exposing pricked skin to a small amount of different substances to find out which one you are allergic to. Treatments for allergies include avoiding the allergy-causing agent, taking medications to reduce the symptoms, immunotherapy, and even emergency epinephrine for an anaphylaxis reaction. Talk to your doctor to find out which allergy treatment is best for you or your child.