Do you break out in hives when a bee stings you? Or do you sneeze every time you pet a cat? If so, you may already have an idea of what is triggering your allergies. Other times, the answer is not as clear what is causing your allergy symptoms. Make an appointment with your doctor for help.

Doctors diagnose allergies in three steps:

1. Personal and medical history. Your doctor will ask you questions to get a complete understanding of your symptoms and their possible causes. Bring your notes to help answer your doctor’s questions. Be ready to talk about your family medical history, the kinds of medicines you take, the symptoms you have, and your lifestyle at home, school, and work.
2. Physical exam. If your doctor thinks you have an allergy, they will pay close attention to your ears, eyes, nose, throat, lungs, and skin during the exam. This exam may include a lung function test to see how well you breathe out air from your lungs. You may also need an X-ray of your lungs or sinuses.
3. Allergy tests to detect sensitivity. Your doctor may do an allergy test to see if your body is making antibodies to a substance. Tests alone do not diagnose allergy. Test results are just one of many tools available to assist your doctor in making a diagnosis.

Sensitivity means your immune system makes IgE antibodies to a substance. These antibodies can then trigger the allergic reaction process. But sometimes, they don’t. So this can mean you may test positive to an allergen, but not have an allergy. This is why doctors use a combination of medical history, physical exam, and allergy tests to make a diagnosis.

What Types of Tests Do Doctors Use to Diagnose Allergies?

Skin Prick Test (SPT)

Skin testing can help confirm many common types of allergies. In some cases, skin tests can be the most accurate and least expensive way to confirm allergens. Skin testing is done in the office and results take 15-20 minutes.

How the SPT test works:
In prick (sometimes called scratch) testing, a small drop of the allergen in question is pricked or scratched on your skin. If your body makes antibodies to that substance, you will develop redness, swelling, and itching at the test site within 20 minutes. You may also see a wheal, which is a raised, round area that looks like a hive. Wheals will itch temporarily. Usually, the larger the wheal, the more the body recognizes the allergen, though this does not always mean it causes more symptoms than something with a smaller wheal.

A positive SPT to an allergen does not necessarily mean you have an allergy. Your allergy specialist must compare the skin test results with your history, to see if the symptoms match the testing.

It is important to know:

• A positive skin test result does not by itself diagnose an allergy.
• A positive skin test does not predict the severity of an allergic reaction.
• A negative skin test usually means you are not allergic.

Specific IgE (sIgE) Blood Test

Blood tests are another way to test for allergies. Both blood and skin tests tell if you make antibody to an allergen. Blood tests can be helpful when people have a skin condition or are taking medicines that interfere with skin testing. They may also be used in children who may not tolerate skin testing.

The allergy blood test is called Specific IgE (sIgE) Blood Testing (known as ImmunoCAP testing). As with skin testing, a positive blood test to an allergen does not necessarily mean that an allergen caused your symptoms, and your doctor has to assess this. This test is a not a good screening test due to the high rates of false positive results.

As with skin testing, a positive blood test to an allergen does not necessarily mean that an allergen caused your symptoms, and your doctor has to assess this.

How the sIgE blood test works:

Your doctor (or the lab) will take a blood sample and send it to be analyzed. Allergens are added to your blood sample to measures the amount of antibodies your blood produces to attack the allergens. The test is reported on a scale of 0.1 to 100 kilounits of antibody. The report may also list allergens by one of 6 classes, depending on how much antibody is detected.

Just like with skin testing, a bigger result means your body is more likely to recognize the allergen. The reported score and class does not reflect how severe the allergy is. There is no skin or blood test that can determine how severe an allergy is for someone.

Physician-Supervised Challenge Tests

A challenge test is the most accurate way to diagnose an allergy. It is the only test that can determine how severe an allergy may be.

How the allergy challenge test works:

In your doctor’s office, you inhale or take a tiny amount of an allergen by mouth. This test is usually done with possible medication or food allergies. A physician, usually an allergist, should supervise this test due to the risk of anaphylaxis, a severe allergic reaction. The dose of allergen is slowly increased over time to see if your body can tolerate it without symptoms. If symptoms begin, the test is stopped and symptoms are treated as needed. The doctor will assess if the symptoms are from the test. If there are no allergy symptoms, it means you are not allergic to that substance.

Intradermal Skin Test

In intradermal (under the skin) testing, the doctor or nurse injects a tiny amount of allergen into the outer layer of skin. The doctor checks your skin after a set amount of time for results, like with the skin prick test. Doctors may use this test if the skin prick test results are negative but they still suspect you have allergies. A doctor may use this test for diagnosing drug or venom allergy.

Patch Test

This test determines what allergen may be causing contact dermatitis. Your doctor will place a small amount of a possible allergen on your skin, cover it with a bandage and check your reaction after 48 to 96 hours. A sensitivity to the substance will cause a local rash.

What Tests Should I Avoid?

Beware of alternative allergy testing methods that are commonly promoted online. Examples include at-home allergy test kits, IgG testing, applied kinesiology (NAET), skin titration, hair analysis. Many of these tests claim to reveal “hidden allergies”. These tests are not recommended by AAFA. They are misleading, provide false information, or are not scientifically proven. See an allergist for appropriate testing and diagnosis.

When Should I See An Allergist?

Allergy symptoms can affect your physical and mental health. If you have symptoms that are affecting your life, reach out to your doctor and ask for a referral to an allergist. With the right allergy treatment plan, your quality of life and health can improve.

Possible allergy symptoms include:

• Itchy eyes, nose, mouth, throat, or skin
• Stuffy or runny nose
• Sneezing, coughing, or wheezing
• Watery eyes
• Hives
• Stomach pain or diarrhea after eating certain foods
• Swelling