How to know what your allergic to

Overview

What is allergy testing?

Healthcare providers perform allergy tests to determine whether your immune system overreacts to certain substances (allergens). If you have an allergic reaction, it means you have an allergy.

People can be allergic to things in the environment like mold, pollen and pet dander. Some people have allergic reactions to bee stings or latex. People with food allergies may not be able to tolerate peanuts, milk or soy.

Why do healthcare providers perform allergy tests?

Your healthcare provider may perform an allergy test if you have allergy symptoms that bother you. Providers also perform allergy tests on people who have asthma. The test can identify allergy triggers that can worsen asthma symptoms or bring on an asthma attack.

You may also need a test if you’ve had a severe allergic reaction called anaphylaxis. This potentially life-threatening problem can cause hives or swelling, breathing difficulty and/or a sharp drop in blood pressure that brings on anaphylactic shock. Your health history along with allergy testing is used to determine the cause of severe reaction. If you have had an anaphylactic reaction or may be at risk for one, then you may need to carry an epinephrine (adrenaline) auto-injector (EpiPen®) to treat the symptoms.

How do I know if I need an allergy test?

If you’re allergic to allergens in the air like dust, pollen or pet dander, you may develop allergic rhinitis. Also known as hay fever, this allergic reaction causes:

• Headaches.
• Itchy, watery eyes.
• Nasal congestion, sneezing or runny nose.
• Shortness of breath, wheezing or chronic cough.
• Sore throat.

Food allergy symptoms typically occur within 30 minutes of food ingestion but may occur up to two hours after ingestion. People with food allergies may experience:

• Skin symptoms such as hives, swelling of the face, lips or tongue, generalized itching.
• Respiratory symptoms such as coughing, wheezing, shortness of breath, chest or throat tightness.
• GI symptoms such as nausea and vomiting, abdominal pain and cramps, vomiting and diarrhea.
• Cardiovascular symptoms such as pale skin, weak pulse, dizziness or lightheadedness.

People who are allergic to latex, fragrances or metals like nickel may develop contact dermatitis. This allergic reaction affects your skin. You may have:

• Burning sensation on skin or blisters.
• Hives and swelling.
• Skin rash or itchy skin.

A patch test, performed by a dermatologist, is used to diagnose these types of reactions.

Test Details

What does an allergy test do?

Allergy tests measure your body’s response to specific allergy triggers or allergens. If you have an allergy, your immune system overreacts. It produces antibodies (proteins) called immunoglobulin E (IgE). These antibodies trigger the release of chemicals that cause an allergic reaction.

What are the types of allergy tests?

There are different ways to test for allergies. Your healthcare provider will select the best method based on your symptoms and the suspected allergens.

These tests include:

• Skin prick (scratch) test: Your provider uses a thin needle to prick the skin on your forearm or back with 10 to 50 different potential allergens. Or your provider may place droplets of potential allergens onto your skin and use a device to scratch and lightly puncture the area, causing the liquid to enter your skin. Reactions such as redness typically occur within 15 minutes of exposure. Your reaction might be a rash or raised, round spots called wheals. This test checks for airborne allergies, food allergies and penicillin allergies.
• Intradermal skin test: You may get an intradermal skin test if skin prick test results are negative or inconclusive. Your provider injects small amounts of the allergen into the outer layer of your skin (epidermis). This test checks for allergies to airborne irritants, medications and insect stings.
• Patch test: This test determines the cause of contact dermatitis. Your provider places drops of an allergen onto the skin on your arm and covers the area with a bandage. Or your provider may apply a patch (bandage) that has the allergen on it. You leave the bandage on and return to the provider’s office within 48 to 96 hours. Then, your provider removes the bandage to check your skin for a rash or other reaction.
• Blood (IgE) test: Your provider sends a sample of your blood to a lab. The lab adds allergens to the blood sample and measures the levels of IgE antibodies in it. Blood tests can have a higher rate of false-positive results.
• Challenge tests: This test occurs only under a provider’s direct, in-person supervision. People with suspected food or drug allergies ingest (swallow) a small amount of an allergen. An allergist, a doctor who specializes in allergies, typically performs this test. Medical supervision is a must. If you develop anaphylaxis, the provider quickly gives an epinephrine injection to stop the reaction.

How should I prepare for an allergy test?

Your healthcare provider will ask you to stop taking allergy medications like antihistamines three to seven days before an allergy test. These medicines can interfere with test results by stopping your immune system’s response to allergens. You should continue to take asthma medication.

What should I expect during an allergy test?

The purpose of skin tests is to see how your body responds to allergens. If you have an allergic reaction, you’ll develop a reaction at the site of the test. Rarely patients may have mild allergy symptoms such as itchy skin, watery eyes and congestion. Most symptoms clear up in one to two hours after the test, the redness or wheals may remain for several more hours.

Are there any risks to getting an allergy test?

The potential for an anaphylactic reaction is the biggest risk. This type of reaction is rare. Providers are always prepared with epinephrine. They offer emergency care if you have a severe reaction during an allergy test.

Are at-home allergy tests effective?

Over-the-counter allergy test kits that you buy at your local drugstore or online aren’t very reliable. Some of them don’t test for the right antibodies. You’re also more likely to get a false-positive result, which may lead you to avoid certain substances or foods unnecessarily.

Health insurers may not fully cover the cost of allergy tests at a healthcare provider’s office. The costs can range from $200 to $1,000. You can ask your insurer about your plan’s policies. In general, it’s best to get allergy tests with a medical expert. They can read the results and discuss treatment options with you.

Results and Follow-Up

When should I get my allergy test results?

You’ll get the results of most allergy tests immediately after testing while at your provider’s office. A patch test can take several days. Results from blood tests sent to a lab may take a week or longer.

What do the results of an allergy test mean?

Allergy test results may be:

• Negative: You aren’t allergic to that substance. It’s rare to get a false (incorrect) negative allergy test result (meaning the test says you don’t have an allergy when you actually do).
• Positive: You’re allergic to that substance. Note that even when tests correctly show that you have an allergy, it doesn’t necessarily mean that you’ll react to that allergen. A false positive test result is possible, especially from a blood (IgE) test. A false positive means the results show you have an allergy when you don’t.

What happens if I have an allergy?

Depending on the allergy, your healthcare provider may recommend one or more of these steps:

• Minimize exposure to allergens: Avoid ones that cause severe reactions, such as latex or certain foods.
• Take daily allergy medications: Antihistamines can prevent or reduce allergic rhinitis and other symptoms.
• Get allergy shots: This type of immunotherapy can decrease the immune system’s response to certain allergens like pet dander. You should get allergy shots for three to five years to experience maximum benefit. Allergy shots can be costly, but they often provide long-lasting relief, even after the shot series is completed.
• Have a medical alert card: A card or medical alert jewelry lets others know about your severe allergy. It tells them you could have an anaphylactic response to peanuts, bee stings or other allergens.
• Carry an epinephrine injection (EpiPen): Keep this medicine with you at all times if you’re at risk for an anaphylactic allergic reaction.

A note from Cleveland Clinic

Allergic reactions can range from annoying congestion to life-threatening anaphylactic shock. Allergy tests can identify substances that cause these types of allergic reactions. There are different allergy tests. Your healthcare provider will choose the best test for you based on symptoms and potential allergy triggers. If you have allergies, you can take steps to get symptom relief.

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