An allergy test is an exam performed by a trained allergy specialist to determine if your body has an allergic reaction to a known substance. The exam can be in the form of a blood test, a skin test, or an elimination diet.
Allergies occur when your immune system, which is your body’s natural defense, overreacts to something in your environment. For example, pollen, which is normally harmless, can cause your body to overreact. This overreaction can lead to:
- a runny nose
- blocked sinuses
- watery eyes
Allergens are substances that can cause an allergic reaction. There are three primary types of allergens:
- Inhaled allergens affect the body when they come in contact with the lungs or membranes of the nostrils. Pollen is the most common inhaled allergen.
- Ingested allergens are present in certain foods, such as peanuts, soy, and gluten.
- Contact allergens must come in contact with your skin to produce a reaction. An example of a reaction from a contact allergen is the rash and itching caused by poison ivy.
Allergy tests involve exposing you to a very small amount of a particular allergen and recording the reaction.
Allergies affect more than 50 million people per year, according to the American College of Allergy, Asthma, and Immunology. Inhaled allergens are by far the most common type. Seasonal allergies and hay fever, which is an allergic response to pollen, affect more than 40 million Americans.
The World Allergy Organization estimates that asthma is responsible for 250,000 deaths annually. These deaths can be avoided with proper allergy care.
Allergy testing can determine what particular pollens, molds, or other substances you’re allergic to. You may need medication to treat your allergies. Alternatively, you can try to avoid your allergy triggers.
Before your allergy test, your doctor will ask you about your lifestyle, family history, and more.
They’ll most likely tell you to stop taking the following medications before your allergy test because they can affect the test results:
An allergy test may involve either a skin test or a blood test. You may have to go on an elimination diet if your doctor thinks you might have a food allergy.
Skin tests are used to identify numerous potential allergens. This includes airborne, food-related, and contact allergens. The three types of skin tests are scratch, intradermal, and patch tests.
Your doctor will typically try a scratch test first. During this test, an allergen is placed on a section of your skin with a special tool that scratches the skin’s surface. You’ll be closely monitored to see how your skin reacts to the foreign substance. If there’s no swelling or redness on the skin, you’re allergic to that specific allergen.
If the scratch test is inconclusive, your doctor may order an intradermal skin test. This test requires injecting a tiny amount of allergen into your skin. Again, your doctor will monitor your reaction.
Another form of allergy skin test is the patch test. This involves using adhesive patches treated with suspected allergens. The patches will remain on your body after you leave your doctor’s office. The patches are then reviewed at 24 hours after application and again at 48 hours if necessary.
If there's a chance you'll have a severe allergic reaction to a skin test, your doctor may call for a blood test. The blood is tested in a laboratory for the presence of antibodies that fight specific allergens. This test, called ImmunoCAP, is very successful in detecting antibodies to major allergens.
An elimination diet can help your doctor determine which foods are causing you to have an allergic reaction. It entails removing certain foods from your diet and later adding them back in. Your reactions will help determine which foods cause problems.
Allergy tests may result in mild itching, redness, or swelling of the skin. Sometimes, small bumps called wheals appear on the skin. These symptoms often clear up within hours but may last for a few days. Mild cortisone creams can alleviate these symptoms.
On rare occasions, allergy tests produce an immediate allergic reaction that requires medical attention. That's why allergy tests should be conducted in an office that has adequate medications and equipment, including epinephrine to treat anaphylaxis, which is a life-threatening allergic reaction.
Call your doctor right away if you develop a severe reaction after you leave the doctor’s office. Call 911 immediately if you have symptoms of anaphylaxis, such as swelling of the throat, difficulty breathing, or low blood pressure. It’s a medical emergency.
Once your doctor has determined which allergens are causing your symptoms, you can work together to come up with a plan for avoiding them. Your doctor can also suggest medications that may ease your symptoms.