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Drug Allergy- Causes, Symptoms, and Treatment

Medikoe Health Expert

Medikoe Health Expert

  Koramangala, bengaluru, karnataka, india, Bengaluru     Feb 9, 2017

   4 min     


What is Drug Allergy?

A drug allergy is the abnormal reaction of the immune system to a certain medication. Any medicines, over the counter prescriptions, are capable of inducing a drug allergy.

The very common symptoms of drug allergy are hives, rash or fever. 

Drug allergy is not the same as a drug side effect and drug toxicity which is caused by an overdose of medication.

Symptoms of Drug Allergy

Symptoms of drug allergy occur within an hour after taking medicine. Other reactions may occur in days or weeks later.

The symptoms of drug allergy include:

  • Skin rash

  • Hives

  • Itching

  • Fever

  • Swelling

  • Shortness of breath

  • Wheezing

  • Runny nose

  • Itchy, watery eyes


Anaphylaxis is a very rare, life-threatening reaction to a drug allergy that causes dysfunction of the body systems. The symptoms of anaphylaxis are-

  • Vomiting

  • Seizure

  • Rapid pulse

  • Loss of consciousness

  • Nausea

  • Abdominal cramps

  • Trouble in breathing

  • Dizziness

Other conditions caused by Drug Allergy

Less common drug allergy reactions occur days or weeks after exposure to a drug. These conditions include:

  • Serum sickness

  • Drug-induced anaemia

  • Drug rash with eosinophilia and systemic symptoms

  • Inflammation in the kidneys

Causes of Drug Allergy

A drug allergy occurs when the immune system by mistake identifies a drug as a harmful substance such as a virus or bacteria. When your immune system detects a drug as a harmful substance, it will develop an antibody specific to that drug. Sometimes an allergy doesn’t develop until there have been repeated exposures.

Drugs commonly linked to Allergies

Any drug can cause an allergic reaction but some drugs are more commonly associated with allergies. The drugs are:

  • Antibiotics, such as penicillin

  • Pain relievers which include aspirin, ibuprofen and naproxen sodium

  • Chemotherapy drugs for treating cancer

  • Medications for autoimmune diseases such as rheumatoid arthritis

Sometimes a drug produces symptoms same as those of a drug allergy, but the drug reaction is not triggered by immune system activity. A few drugs that are commonly associated with this condition include:

  • Aspirin

  • Dyes used in imaging tests

  • Opiates for treating pain

  • Local anaesthetics

Who can you prevent Drug Allergy?

If you have a drug allergy then you should try to avoid the drug. Make sure that the particular drug is identified in your medical records.

Try wearing a medical alert bracelet that identifies your drug allergy.

Diagnosis of Drug Allergy

In studies it has found that drug allergies may be overdiagnosed and that patients may report drug allergies that have never been confirmed. The doctor will do the physical examination and ask you about your medical history. The doctor will ask you about your symptoms, the time you took medications. 

The doctor may ask for other tests which include the following:

Skin tests

In a skin test, the allergist administers a small amount of a suspect drug to your skin either with a tiny needle, an injection or a patch. A positive reaction to a test will cause a red, itchy, raised bump and suggests that you may have a drug allergy.

A negative result suggests that you are not allergic to that particular drug.

Blood tests

The doctor may order blood tests for detecting allergic reactions to certain drugs.

These tests are not performed often because of limited research on their accuracy.

What does the result of diagnosis say?

The doctor after analyzing your results can reach on one of the following conclusions:

  • You have a drug allergy

  • You don’t have a drug allergy

  • You may have a drug allergy, with varying degrees of certainty

With the help of these conclusions, the doctor makes future treatment decisions.

Treatment of Drug Allergy

Drug allergy can be treated in two ways:

  • Treatment for present allergy symptoms

  • Treatment that may enable you to take an allergy-causing drug if it is medically necessary

Treating current symptoms

The following methods are used to treat an allergic reaction to a drug:

Withdrawal of the drug- If the diagnosis to any particular drug comes positive then the doctor may ask you to discontinue the drug. In many cases, this may be the only treatment for drug allergy.

Antihistamines- The doctor may recommend antihistamines to block immune system chemicals activated during an allergic reaction.

Corticosteroids- Oral or injected corticosteroids are used to treat inflammation associated with more serious reactions.

Treatment of Anaphylaxis- The treatment of anaphylaxis requires an immediate injection as well as hospital care to maintain blood pressure and support breathing.

Taking allergy-causing drugs

If you are allergic to any drug your doctor will not prescribe that drug until necessary.  The doctor provides careful supervision, and supportive care to treat an adverse reaction.

Graded challenge

If the drug allergy diagnosis is uncertain then the doctor may recommend a graded drug challenge. In this procedure, the doctor gives you two to five doses of the drug, starting with a small dose and increasing to the desired dose. 

Drug Desensitization

If it is necessary to take the drug which causes allergic reaction then the doctor may recommend a treatment called drug desensitization. In this treatment, a very small dose and then gradually larger doses every 15 to 30 minutes over several hours or days is administered. If you reach the desired dosage with no reaction then you can continue the treatment.


Tags:  Allergies ,Drug Allergy, Penicillin

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