An allergic reaction occurs when the body's immune system mistakenly identifies a harmless substance, such as pollen, pet dander, or certain foods, as a threat. This triggers the immune system to release chemicals, including histamine, which can cause symptoms like sneezing, itching, hives, 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 nuts, shellfish, latex, and certain medications. People with allergies may need to avoid these triggers and carry emergency medications, such as epinephrine, to manage severe reactions. Understanding and recognizing the signs of an allergic reaction can help individuals seek timely treatment and prevent complications.