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An allergy is when your body’s immune system reacts to something that’s normally harmless to most people. If you come into contact with a substance (allergen) that your immune system views as a threat, it responds by releasing a chemical called histamine. The release of histamine is what causes the reactions you feel, and where you experience the reaction depends on where histamine was released in your body. For example, if you’re allergic to something you breathe in—like pollen, dust mites, animal dander or mold—your nose, lungs and eyes could be where you are most likely to have symptoms. If you’re allergic to any food, you may experience symptoms in your mouth or digestive system.
Allergies exist in several different forms, but many fall into larger buckets like seasonal, year-round, food or bee, wasp, and hornet allergies.
Spicy food can make your nose run, and a bug bite can be annoyingly itchy. Most people experience reactions like these from time to time. These reactions are usually sensitivities or intolerances, but they could also be related to allergies. Anything you come into contact with (allergens) could cause an allergic reaction if your immune system views it as a threat and responds by releasing histamine, along with other substances released by the body.
Certain substances are frequently responsible for allergic reactions. Some of the most common types of allergies include the below: