Are Allergy Tests Accurate for Diagnosing Allergies?

Yes, allergy tests can be wrong. Any type of allergy test—including skin prick tests, blood tests, and skin patch tests—has the potential to return false-negative or false-positive results. A false-negative result means that the test came back negative, but there was actually an allergy; a false-positive result means that the test came back positive when there was no allergy.

False-negative allergy test results are quite rare, but it is still possible in certain situations. A result may be false-negative if the test is designed to detect allergens to which the patient is not allergic; if the patient is allergic to allergens that are not tested for, the result could be negative, falsely indicating there is no allergy.

While there are no limitations on the frequency of allergy testing, retesting every two years is typically considered reasonable. However, there are certain circumstances that can affect this decision, including if new allergy symptoms arise, if current allergy symptoms worsen or do not improve with treatment, or if medications do not provide adequate relief.

The various allergy tests provide different levels of accuracy, depending on the unique circumstances of each situation.

• Skin Prick Test — Commonly referred to as SPT, the skin prick test is one of the most common allergy tests performed. Skin tests are thought to be the most accurate and inexpensive methods to confirm allergens, which involve gently pricking the skin on the arm or back with suspected allergens. Results are ready in as little as 20 minutes, and the doctor will observe the reactions.

• Blood Tests — Blood tests, which are available in many forms, are another common way to measure the presence of an allergy. The most popular blood tests include radioallergosorbent testing (RAST), ImmunoCAP testing, and the ELISA test. Blood tests typically detect the presence of certain antibodies in the blood, which can determine the type as well as the severity of the allergy.

• Food Challenge and Elimination Testing — In certain situations, an allergist may recommend a food challenge and elimination test. This involves eliminating certain foods that are suspected to cause allergies but can also involve restricting one’s diet and slowly introducing certain foods back into the diet. Although this test is riskier compared to the above-discussed allergy tests, as moderate to severe allergic reactions may occur, it is the most accurate method used in diagnosing food allergies. This type of test is best performed under medical supervision, which allows any complications to be observed and treated right away, should they arise.
 
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