Allergies

Allergies occur when your immune system reacts to a foreign substance — such as pollen, bee venom or pet dander — that doesn't cause a reaction in most people.

Your immune system produces substances known as antibodies. Some antibodies protect you from unwanted invaders that could make you sick or cause infection.

When you have allergies, your immune system makes antibodies that identify a particular allergen as harmful, even though it isn't. When you come into contact with the allergen, your immune system's reaction can inflame 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 most allergies can't be cured, a number of treatments can help relieve your allergy symptoms.

Tests and diagnosis

To evaluate whether you have an allergy, your doctor may:

  • Ask detailed questions about signs and symptoms
  • Perform a physical exam
  • Have you keep a detailed diary of symptoms and possible triggers

If you have a food allergy, your doctor may:

  • Ask you to keep a detailed diary of the foods you eat
  • Have you eliminate a food from your diet (elimination diet) — and then have you eat the food in question again to see if it causes a reaction

Your doctor may also recommend one or both of the following tests:

  • Skin test. Your skin is pricked and exposed to small amounts of the proteins found in potential allergens. If you're allergic, you'll likely develop a raised bump (hive) at the test location on your skin. Allergy specialists usually are best equipped to perform and interpret allergy skin tests.
  • Blood test. A blood test that's sometimes called the radioallergosorbent test (RAST) can measure your immune system's response to a specific allergen by measuring the amount of allergy-causing antibodies in your bloodstream, known as immunoglobulin E (IgE) antibodies. A blood sample is sent to a medical laboratory, where it can be tested for evidence of sensitivity to possible allergens.

If your doctor suspects your problems are caused by something other than an allergy, you may need other tests to identify — or rule out — other medical problems.

Treatments and drugs

Allergy treatments include:

  • Allergen avoidance. Your doctor will help you take steps to identify and avoid your allergy triggers. This is generally the most important step in preventing allergic reactions and reducing symptoms.
  • Medications to reduce symptoms. Depending on your allergy, allergy medications can help reduce your immune system reaction and ease symptoms. Medications can include over-the-counter or prescription medications in the form of oral medications, nasal sprays or eye drops.
  • Immunotherapy. For severe allergies or allergies not completely relieved by other treatment, your doctor may recommend allergen immunotherapy. This treatment involves a series of injections of purified allergen extracts, usually given over a period of a few years.

Another form of immunotherapy is a tablet that's placed under the tongue (sublingual) until it dissolves. Sublingual drugs are used to treat some pollen allergies.

  • Emergency epinephrine. If you have a severe allergy, your doctor may give you an emergency epinephrine shot to carry with you at all times. Given for severe allergic reactions, an epinephrine shot (EpiPen, Auvi-Q, others) can reduce symptoms until you get emergency treatment.