Final answer:
Allergies occur when the immune system overreacts to harmless substances, causing symptoms primarily in the respiratory system. Treatment options include antihistamines, epinephrine for severe reactions, and immunotherapy to desensitize the immune system.
Step-by-step explanation:
Allergies occur when the immune system overreacts to normally harmless substances in the environment, resulting in a variety of symptoms. The immune system mistakenly identifies these substances, known as allergens, as harmful and releases chemicals to defend against them. This immune response primarily affects the respiratory system, causing symptoms such as sneezing, itching, and runny nose. Allergic symptoms can appear immediately or within a few hours after exposure to the allergen and can range from mild to severe.
For mild allergy symptoms, antihistamines can be used to reduce symptoms by counteracting the histamines released during the allergic response. Severe systemic allergic reactions, called anaphylaxis, require immediate medical attention and are treated with injections of epinephrine. Immunotherapy is another treatment option, which involves gradually exposing the immune system to increasing amounts of allergens to desensitize it over time.