What are allergies? Allergies are caused by an exaggerated response by the body’s immune system to a particular substance, called an allergen. Allergies, also called allergic reactions, are common and include food allergies, allergic conjunctivitis, respiratory allergies, insect bite allergies, drug allergies, and skin allergies. Skin allergies are linked to conditions, such as eczema and contact dermatitis. Allergies are also associated with asthma and other respiratory problems. The immune system is made up of special cells that circulate throughout the body to defend the body against foreign substances, such as viruses and bacteria. If you have allergies, your immune system overreacts when you inhale, swallow or touch normally harmless substances, such as pollen or dust. This results in the release of powerful mediators like histamine, which causes the swelling, inflammation, and itching of affected tissues. People with allergies are often allergic to more than one substance. Common allergies include those to dust, pollen, mold spores, animal dander, bee stings, and cockroach or dust mite droppings. Some people have allergies to certain plants; medications, such aspirin or penicillin; foods, such as eggs or milk; or chemicals and other substances, such as latex. A very common type of allergy is hay fever, which is an allergy to pollen. Hay fever and other respiratory allergies, such as allergies to mold and dust, are types of allergic rhinitis. Symptoms of these allergies can mimic the symptoms of a cold and include runny nose and sneezing. Symptoms of other types of allergies can affect the respiratory system, the gastrointestinal system, and the skin. Diagnosis and treatment of allergies can control symptoms of allergies to a degree that allows you to live a full and active life. Treatment may include a combination of lifestyle changes, medications and other measures. Allergic reactions can range in severity from mild to life threatening. Seek prompt medical care if you, or your child, have symptoms of allergies, such as sneezing, watery eyes, nasal congestion, rash, or nausea and vomiting after eating certain foods. An anaphylactic reaction is an immediately life-threatening type of allergic reaction characterized by a swollen tongue (and swelling in general), combined with hives, itching, shortness of breath, and rapid breathing (more than about 16 breaths per minute for an adult). The reaction is sudden, severe and can include respiratory distress. Seek immediate medical care (call 911) if you, or someone you are with, have symptoms of an anaphylactic reaction or other serious allergic reaction, even if there is no history of allergies.