At least 50 million Americans have some type of allergy. Depending on the severity, allergies can be a nuisance or they can even be life-threatening. Allergy testing is a tool used to determine if the body reacts to a certain substance. There are various types of allergy tests.
What is Allergy Testing?
An allergy occurs when the immune system overreacts to a substance, causing a heightened immune response. The substance is generally harmless, but repeated exposures will cause this reaction again.
Symptoms of allergies include:
- Runny nose.
- Itchy, watery eyes.
- Blocked sinuses.
Anything can be an allergen, which is the substances that causes an allergic reaction. However, allergens can generally be broken down into three categories:
- Inhaled allergens: These allergens cause symptoms when exposed to the mucus membranes of the nose and lungs. An example is pollen.
- Ingested allergens: These allergens cause symptoms when consumed. An example is peanuts.
- Contact allergens: These allergens cause symptoms when the allergen meets the skin. An example is poison ivy.
Allergies can often be diagnosed using allergy testing. There are various types of allergy tests, but the most common types expose the patient to tiny amounts of potential allergens to check for a reaction. A treatment plan is devised based on the results.
How Does Allergy Testing Work?
There are three main types of allergy tests.
1. Skin Tests
Skin tests can check for many allergies at one time. There are three types of skin tests available: scratch, intradermal and patch tests.
Typically, a scratch test is performed first. The scratch test involves placing a tiny amount of the allergen in a liquid. The liquid is placed on a tiny tool that punctures the skin and places this allergen into this area. Monitoring occurs while waiting for reactions. If any redness, swelling or elevation is noted at the site, the patient is said to be allergic to that allergen.
If the scratch test is inconclusive or shows minimal results, an intradermal test will be performed. Tiny amounts of the allergen are injected into the top layer of the skin. If any redness, swelling or elevation is noted at the site, the patient is said to be allergic to that allergen.
The patch test uses special patches that are already loaded with allergens. These patches are placed on the skin and the patient can the leave the office. The patient returns after 48 hours to review the sites, then again at 72 to 96 hours.
2. Blood Tests
Blood tests are helpful for those who may have a severe allergy and are at-risk during a skin test. They are also helpful for children and those who may not be able to sit still for a long duration for a skin test. However, a blood test is typically pricier than a skin test. Blood tests detect IgE antibodies for major allergens.
3. Elimination Diets
Elimination diets are often recommended for those with suspected food allergies. An elimination diet involves removing foods that may be causing an allergic reaction, then adding them back in to see if they cause symptoms.
What to Expect After an Allergy Test
After testing, results will be reviewed. If doing skin testing — scratch and/or intradermal — results should be available by the end of the appointment. Patch-testing results should be available once the patches are removed. Blood testing results take longer — up to several weeks.
Allergy shots are often recommended based on the results of the allergy test. The goal of allergy shots is to desensitize the patient to what they are allergic to by giving them small, incremental doses of the substances they are allergic to, with the goal of reducing symptoms over time.
Allergy shots are made by combining several of the allergens into a shot, or several shots. During the build-up phase, they are typically given in the arm weekly. With each shot, the dosage is increased. Once the dosage has increased to its maximum strength, the maintenance phase has begun — maintenance can last up to five years, with shots required about every month.
Allergy shots are not without risk; though most people have minimal symptoms with their shots, reactions can occur.
- Local reactions: Redness, swelling and irritation can occur at the injection site. These reactions occur within a few hours after the injection, but clear up shortly after.
- Systemic reactions: Sneezing, nasal congestion and hives occur with a systemic reaction.
- Anaphylaxis: Anaphylaxis is a life-threatening allergic reaction. It typically begins within 30 minutes of the allergy shot and must be treated immediately.
After receiving an allergy shot, the patient typically must remain in the office for 30 minutes to observe for a reaction. Reactions are reported to medical staff immediately.