An allergy is an abnormal reaction by a person’s immune system against a normally harmless substance, such as pollen, pet dander, or dust mites. When a person who is allergic encounters these triggers, the body reacts by releasing chemicals which cause allergy symptoms. The severity of allergies varies from person to person and can range from minor irritation to anaphylaxis – a potentially life-threatening emergency. While allergies can’t be cured, a number of treatments can help relieve your symptoms.