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
- itchy, 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 or throat. Pollen is the most common inhaled allergen.
- Ingested allergens are present in certain foods, such as peanuts, soy, and seafood.
- 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 living in the USA, 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, as asthma is considered an allergic disease process.
Allergy testing can determine which 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.
How to prepare
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:
- prescription and over-the-counter antihistamines
- certain heartburn treatment medications, such as famotidine (Pepcid)
- anti-IgE monoclonal antibody asthma treatment, omalizumab (Xolair)
- benzodiazepines, such as diazepam (Valium) or lorazepam (Ativan)
- tricyclic antidepressants, such as amitriptyline (Elavil)
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 in liquid, then that liquid is placed on a section of your skin with a special tool that lightly punctures the allergen into the skin’s surface. You’ll be closely monitored to see how your skin reacts to the foreign substance. If there’s localized redness, swelling, elevation, or itchiness of the skin over the test site, 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 the dermis layer of your skin. Again, your doctor will monitor your reaction.
Another form of skin test is the patch test (T.R.U.E. TEST). This involves using adhesive patches loaded with suspected allergens and placing these patches on your skin. The patches will remain on your body after you leave your doctor’s office. The patches are then reviewed at 48 hours after application and again at 72 to 96 hours after application.
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 IgE antibodies to major allergens.
An elimination diet may 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, and 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 topical steroid creams can alleviate these symptoms.
On rare occasions, allergy tests produce an immediate, severe 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 potentially life-threatening acute allergic reaction.
Call your doctor right away if you develop a severe reaction right after you leave the doctor’s office.
Call 911 immediately if you have symptoms of anaphylaxis, such as swelling of the throat, difficulty breathing, a fast heart rate, or low blood pressure. Severe anaphylaxis is 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.