Allergy is a medical condition in which the immune system reacts abnormally to certain substances, known as allergens, that are typically harmless to most people. Common allergens include pollen, dust mites, pet dander, certain foods, and insect venom. When a person with allergies comes into contact with an allergen, their immune system produces antibodies that trigger the release of chemicals such as histamine, leading to symptoms such as sneezing, itching, hives, swelling, or difficulty breathing. Allergies can range from mild to severe, and in some cases can be life-threatening (anaphylaxis). Treatment for allergies may include avoidance of allergens, medications such as antihistamines or corticosteroids, and in severe cases, allergen immunotherapy. Research in the field of allergy aims to better understand the mechanisms behind allergic reactions, develop more effective treatments, and improve allergy management and prevention strategies.