Drug Allergy

In a true drug allergy, the immune system overreacts to a medication, triggering the production of antibodies to fight off the foreign “invader.” This causes the release of histamines and other chemicals in the body, which result in drug allergy symptoms. Allergic and non-allergic drug reactions may prove difficult to distinguish from each other. Non-allergic drug sensitivities can have similar symptoms but do not involve the immune system. Regardless of what is behind a drug reaction, all abnormal drug responses should be evaluated by an allergist.


Symptoms of a severe drug allergy typically appear within an hour. Milder reactions can manifest hours to even weeks later. Signs of a drug allergy include:

  • Hives (urticaria)
  • Itching
  • Facial swelling
  • Respiratory problems
  • Fever
  • Dizziness
  • Itchy, watery eyes
  • Congestion
  • Vomiting and diarrhea
  • Anaphylaxis – A life-threatening allergic reaction requiring immediate medical attention. Any of the above symptoms can result, followed by dangerously low blood pressure and breathing trouble that can send your body into shock.


Once your immune system decides a medication is an enemy, it creates targeted antibodies to fight back. The next time you take that drug, the antibodies release armies of histamines to rid your body of the drug, thus causing the allergic reaction.

Certain drug classes are most often behind drug allergies, including:

Diagnosis & Treatment Options

Research suggests that drug allergies are overdiagnosed, which is one reason a conclusive diagnosis is essential. Many people needlessly avoid drugs that may be the best course of treatment for a given condition. The physicians at Stone Oak Allergy have extensive training and experience pinpointing allergens and designing personalized treatment plans.

The doctor will perform a physical exam and discuss your medical history and allergy symptoms. Testing options vary by drug and include skin test, blood test, and oral drug challenge (patients ingest increasing amounts of a drug until a reaction is seen or tolerance can be determined). Often, a final analysis clearly indicates you either do or do not have a drug allergy. However, a gray area exists in drug allergy diagnosis, and you could hear that the data is not conclusive either way, meaning you might have a drug allergy. The latter conclusion is still useful information, and we can help you navigate any of these paths!

Treatment depends on severity of the allergy and the type of drug involved. In most instances, allergen avoidance is key, and your doctor can prescribe an alternative medication. When no satisfactory alternative exists, a desensitization process may result in reduced sensitivity so you can start taking the drug again. This procedure can only occur in the office with medical supervision. It involves taking a small dose of the drug and gradually increasing the dose over a number or days until you can tolerate a therapeutic dose.

If your allergic reaction is on the milder end of the spectrum, your allergist may prescribe some medications that can block your body’s immune response and control allergy symptoms.

Stone Oak Allergy’s physicians will partner with you to determine how best to protect you from drug allergy issues. Book an appointment with an experienced Stone Oak Allergy Physician today!

Drug Allergy Facts