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Drug Allergy Testing

An accurate diagnosis of a possible drug allergy is essential, especially with antibiotics. Research has indicated that drug allergies may be overdiagnosed, causing patients to report drug allergies that have never been confirmed. This has led to the widespread use of pricier, less appropriate drugs, such as a stronger antibiotic for mild infections. At Frontier Allergy Asthma and Immunology, we can help you determine if you truly have a drug allergy.
Common triggers of drug-related allergies include penicillin and related antibiotics, drugs containing sulfonamides (sulfa drugs), anticonvulsants, nonsteroidal anti-inflammatory drugs (NSAIDs such as aspirin and ibuprofen), chemotherapy drugs, and imaging contrast dye. Do not confuse a drug allergy with a drug side effect or with drug toxicity! A drug side effect is a known possible reaction that is listed on a drug label. Drug toxicity is caused by an overdose of medication.

Diagnosis of a Drug Allergy

After a discussion of your medical, allergy, and family history, your allergy specialist will perform a physical exam and determine which testing method(s) to use.

Skin Testing

Patients may either undergo a skin prick test or an intradermal skin test. During a skin prick test, a small amount of a suspect drug is administered to the skin and scratched with a plastic applicator. During an intradermal skin test, a small amount of a suspect drug is injected just under the skin using a small needle. Both of these tests require a 15-20 minute wait for the skin to react, followed by physician observation for raised, red, itchy bumps (called wheals). A positive result generally indicates a drug allergy, but a negative skin test does not definitively rule out an allergy to a drug. However, at Frontier Allergy Asthma and Immunology, your physician will take the necessary next steps to help you determine whether or not you may have a true drug allergy.

Patch Testing

If you do not have an immediate allergic reaction to any drug(s) during the physician-supervised skin test, your doctor may recommend undergoing a patch test. Patch testing is a way for your doctor to observe any delayed allergic reactions you may have to certain drugs. A patch test involves taping a small amount of the drug in a chamber onto the back. After 48-72 hours of keeping the area dry and undisturbed, you will return to the office for patch removal and examination of your results.

Oral Drug Challenge

Based on the results of your previous tests, your doctor may recommend undergoing an oral drug challenge. This test is performed in a healthcare setting under your physician’s supervision. In this challenge, you will ingest increasing amounts of a drug until a reaction occurs (for which you will immediately be treated with medication) or tolerance can be verified.


After an analysis of your symptoms and test results, your doctor should be able to definitively indicate whether you have a drug allergy or not. Very uncommonly, test results can be inconclusive, and your doctor will indicate that you may have a drug allergy. If this is the case, do not worry. Your test results still provide useful information, and your doctor will let you know how to move forward with treatment and prevention.

Next steps

If you are interested in further discussion about your specific needs, Dr. Reshamwala is happy to see you and answer any questions you may have. Please call (512) 535-2655 or email to schedule an appointment today! Book an appointment

Written by: Dr. Neha Reshamwala
NPI number: 1780874578
Page last reviewed: 03/20/21

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