Allergies are among the most common of medical disorders. It is estimated that 60 million Americans, or more than one in every five
people, suffer from some form of allergy.
An allergy is a hypersensitivy disorder of the immune system.
How do you get allergies? Scientists think both genes and the environment have something to do with it. Normally, your immune system fights germs. It is your body’s defense system. In most allergic reactions, however, it is responding to a false alarm.
Allergies occur when your immune system reacts to a foreign substance such as pollen, bee venom or pet dander. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid.
Your immune system produces substances known as antibodies. Some of these antibodies protect you from unwanted invaders that could make you sick or cause an infection. When you have allergies, your immune system makes antibodies that identify your particular allergen as something harmful, even though it isn’t. When you come into contact with the allergen, your immune system’s reaction inflames your skin, sinuses, airways or digestive system.
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 allergy symptoms.
Mild allergies like hay fever are very common in the human population, and cause symptoms, such as red eyes, itchiness, and runny nose, eczema, hives, or an asthma attack. In some people, severe allergies to environmental or dietary allergens or to medication may result in life-threatening reactions called anaphylaxis. Food allergies, and reactions to the venom of stinging insects are often associated with these severe reactions.
A variety of tests exist to diagnose allergic conditions. These include placing possible allergens on the skin and looking for a reaction such as swelling. Blood tests can also be done to look for an allergen-specific IgE.
Treatments for allergies include avoiding known allergens, use of medications such as anti-histamines that specifically prevent allergic reactions, steroids that modify the immune system in general, and medications such as decongestants that reduce the symptoms. Many of these medications are taken by mouth, though epinephrine, which is used to treat anaphylactic reactions, is injected. Immunotherapy uses injected allergens to desensitize the body’s response.
Allergic diseases are more common in industrialized countries than in agricultural countries , and there is a higher rate of allergic disease in urban populations versus rural populations.