The meaning of ALLERGIC is of, relating to, affected with, or caused by allergy. How to use allergic in a sentence. Allergies are your immune system’s overreaction to foreign substances. When you touch, inhale or eat something you’re allergic to, your body thinks it’s harmful and reacts to try to get rid of it. This can cause minor reactions like itching, sniffling and sneezing. Allergic reactions can cause swelling, hives, rashes, and anaphylaxis in severe cases. Learn about allergy testing, symptoms, causes, treatment, and prevention. Allergies happen when the immune system reacts to a foreign substance that gets inside the body. These substances are known as allergens. They include pollen, bee venom and pet dander. Allergies also can happen due to certain foods and medicines that don't cause reactions in most people. What is an allergic reaction? Allergic reactions are a set of symptoms that happen after you touch, inhale or eat something you’re allergic to. They can also happen after a bee sting. Examples of allergens that can set off allergic reactions include pollens, pets, dust, foods and medications. The mechanism of allergic reactions involves immunoglobulin E antibodies (IgE) binding to an allergen and then to a receptor on mast cells or basophils, where they trigger the release of inflammatory chemicals such as histamine. [16] Diagnosis is typically based on a person's medical history. [3] Allergies can cause a variety of symptoms such as a runny nose, sneezing, itching, rashes, swelling, or asthma. Allergies can range from minor to severe. Anaphylaxis is a severe reaction that can be life-threatening. Doctors use skin and blood tests to diagnose allergies. Learn about different types of allergies, allergic reactions, their types, symptoms, and severity. Allergic reactions can affect your eyes, skin, breathing or more. If you were having one, would you know it? WebMD tells you what you need to know. How do I know if I have allergies and what I’m allergic to? If you suffer from a runny nose, sneezing, or red, watery eyes, you may have allergies. But how do you know for sure? And how do you find out exactly what you’re allergic to?.