An allergy is an overreaction of the immune system to substances that are generally considered harmless to most people. These substances, called allergens, can include pollen, house dust, dairy products, insect poisons, certain foods, medicines, and others.

In an allergic reaction, the immune system makes a mistake and begins to produce antibodies, causing various symptoms. These symptoms can range from mild to severe and can include itching, skin rashes, runny nose, cough, burning eyes, swelling, and even anaphylactic shock, which is a serious and potentially fatal reaction.

Treating allergies can include avoiding allergens, taking antihistamines, inhalers, and even allergen-specific immunotherapy. Allergies can have a significant impact on quality of life, and therefore it is important to consult a doctor for proper diagnosis and management of this condition.