An allergic reaction occurs when the body's immune system mistakenly identifies a harmless substance, like pollen or peanuts, as a threat. This triggers the immune system to release chemicals, such as histamine, which can cause symptoms like sneezing, itching, or swelling. In some cases, allergic reactions can be severe and lead to anaphylaxis, a life-threatening condition that requires immediate medical attention. Common allergens include dust mites, animal dander, and certain foods. People with allergies may need to avoid these triggers to prevent reactions. Treatments, such as antihistamines or allergy shots, can help manage symptoms and improve quality of life.