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Drug Allergy

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A drug allergy is an abnormal reaction your immune system produces in response to an otherwise harmless medication. Any medication is capable of inducing a drug allergy, though drug allergies are more likely with certain medications. It may be easy to mistake allergic and non-allergic drug reactions with one another, as symptoms may overlap. However, non-allergic drug sensitivities have no immune system involvement. Regardless, all abnormal drug responses that deviate from drug label side effects require evaluation by an allergy specialist. At Frontier Allergy Asthma and Immunology, our allergist has extensive knowledge and experience to help diagnose and treat your drug allergy.
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.

Symptoms of a Drug Allergy

Drug allergy symptoms that occur within the first hour of taking the drug may include:

  • Skin rash, hives, itching, and/or swelling
  • Fever
  • Shortness of breath, wheezing, or sensation of pressure on the chest
  • Runny nose or postnasal drip (sensation of mucus running down the back of the throat)
  • Itchy, watery eyes
  • Anaphylaxis (a rare, life-threatening reaction that may involve difficulty breathing, bodily swelling, abdominal issues, dizziness, drop in blood pressure, weak but rapid pulse, or loss of consciousness)

Delayed drug allergy symptoms (though less common) can occur days after exposure to a drug, including:

  • Serum sickness
  • Drug-induced anemia
  • Drug rash with eosinophilia and systemic symptoms (DRESS)
  • Inflammation in the kidneys (nephritis)

These delayed drug allergy symptoms may persist for some time after you discontinue use of the drug causing these symptoms.

Causes of a Drug Allergy

A drug allergy arises when your immune system mistakenly identifies a drug as a harmful substance. Normally, harmful substances include viruses or bacteria. However, once your immune system deems a drug harmful to the body, it develops specific antibodies that will direct your immune system to attack the substance. The chemicals released by this activity causes the symptoms associated with an allergic reaction. Drugs that are commonly linked to drug allergies include:

  • Antibiotics, especially penicillin (and related antibiotics)
  • Non-steroidal anti-inflammatory drugs, such as aspirin and ibuprofen
  • Drugs containing sulfonamides (sulfa drugs), such as naproxen sodium
  • Chemotherapy drugs for the treatment of cancers
  • Medications used to treat autoimmune diseases
  • Anticonvulsants

Drugs that are commonly linked to nonallergic drug reactions (which involves similar symptoms that occur separately from the immune system) include:

  • Aspirin
  • Contrast dyes used in imaging tests
  • Opiates for treating pain
  • Local anesthetics

Diagnosis and Treatment of a Drug Allergy

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. During your visit, your allergy specialist will discuss your medical, allergy, and family history and perform a physical examination. With this information, your allergy specialist will be able to determine which testing method(s) may work best to determine whether you have a drug allergy or not. Common testing options include a skin test, blood test, patch test, or an oral drug challenge. Your doctor may suggest you undergo one or more of these tests, and a final analysis commonly indicates whether you do or do not have a drug allergy. However, in rare cases, your test results may be inconclusive, meaning you may have a drug allergy. Although this can be frustrating for some patients, do not despair, as this is still useful information that your doctor can use to recommend treatment and prevention options. Treatment of your drug allergy depends on the severity of the allergy and the type of drug that causes allergic symptoms. Your allergist will likely suggest the prevention of symptoms through drug avoidance or a medically-supervised desensitization process. A desensitization treatment involves taking small, but incrementally increasing doses of the drug over a number of days until a therapeutic dose can be adequately tolerated.

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 512-382-1933 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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