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All you Need to Know about Drug Allergy: Symptoms, Causes, and Treatment


Allergens are not necessarily dusted particles or other foreign particles only. Medication can cause allergies in some people. The immune system treats the drug or medication as a foreign substance, leading to reactions like hives or rashes, bowel disturbance, difficulty breathing, etc. This reaction is referred to as a drug allergy.

Taking too much of a particular medication causes adverse drug reactions (ADRs). It can also occur if the medication taken reacts with another drug in your system. However, this allergic reaction subsides often after a day or two when the medication has been discontinued.

Drug allergies are rather annoying and severe; on rare occasions, anaphylaxis is a painful condition that affects multiple body parts, and loss of consciousness may occur. Other life-threatening responses to medication include dizziness and abdominal cramping.

A person will experience drug allergy at any point in their life, but women have more reactions than men, while the elderly and children have less similar responses.

What are the Symptoms of Drug Allergy?

Most of these signs and symptoms may occur within an hour after the drug is administered. They may also occur weeks after exposure to the medication in a delayed type of allergy called serum sickness.

The most common symptoms of a drug allergy include:

  • Skin rashes
  • Itching
  • Hives
  • Fever
  • Watery and itchy eyes
  • Running nose
  • Short breaths
  • Swelling of the face, lips, and or tongues


The condition is life-threatening and may cause organ or tissue dysfunction. The signs and symptoms include:

  • Throat and airway tightening that causes trouble in breathing
  • Abdominal cramps
  • Nausea
  • Diarrhea
  • Vomiting
  • Lightheadedness or dizziness
  • Rapid and weak pulses
  • Blood pressure drops
  • Seizures
  • Loss of consciousness

Apart from sickness serum, which occasionally affects the joints, causing pain and fever, swelling, rash, and nausea, other conditions are associated with drug allergy and their symptoms.

  1. Drug-Induced Anemia – This is a reduction in the number of red blood cells in the body, which causes irregular heartbeats, fatigue, and breath shortness
  2. Kidney Inflammation (Nephritis) – Causes fever, general swelling, confusion, blood in urine, and other symptoms.
  3. Drug rash with eosinophilia and systematic symptoms (DRESS) – Causes rash, high counts of white blood cells, swelling, hepatitis infection recurrence

What Causes Drug Allergy?

The development of drug allergies occurs when the sensitivity of your immune system extends to identifying drugs as harmful. The first time the drug is taken, the body reads it as a foreign substance, and a specific antibody to the drug is developed.

The second time the drug is taken, the antibodies flag it and attack the particle through the immune system. During the process, the chemicals released cause the symptoms associated with the drug allergy.

Sometimes, an allergic reaction occurs the first time you take the medication. This rare case occurs when the drug binds directly to a white blood cell known as a T cell and sets a motion involving a chemical release that causes the allergic reaction.

Any drug can cause a negative response in your body, although some are more prone to the condition. These drugs include:

  • Some antibiotics, like penicillin
  • Non-steroidal Anti-inflammatory Drugs (NSAIDs) and aspirin
  • Most chemotherapy drugs for cancer treatment
  • Auto-immune medications for diseases like rheumatoid arthritis
  • Corticosteroidal lotions or creams
  • Anti-retroviral drugs, such as HIV or AIDS medications
  • Echinacea
  • Pollen grains

Drug allergy symptoms may be confused with symptoms of a condition referred to as pseudoallergic drug response or non-allergenic hypersensitivity. The allergic reaction is caused by a reaction to a drug, which produces signs and symptoms akin to drug allergy, but not caused by the immune system activity.

Drugs causing non-allergenic hypersensitivity include:

  • Imaging tests dyes
  • Aspirin
  • Pain management opiates
  • Local anesthetics

What are the Risk Factors of Drug Allergy?

Several factors increase the risks of drug allergy. Some of them include:

  • History of other allergic reactions like hay fever or food allergy
  • Allergic reactions to other drugs
  • Family history of the condition
  • Prolonged exposure to drugs as a result of high doses, overdose, repetitive use of the drug, or an extended use
  • Some illnesses typically associated with the drug reactions, such as HIV or the Epstein-Barr virus

Drug Allergy Diagnosis

Accurate diagnosis of drug allergy results from a thorough and appropriate examination. Incidentally, drug allergies are overdiagnosed, which leads to patients reporting cases that have never been confirmed. A misdiagnosis of drug allergy often results in inappropriate and possibly expensive drugs.

The doctor will ask you questions during a diagnosis and conduct a physical examination. The points that help in the diagnosis are details of the onset of the signs and symptoms, when the drug was administered, how the medication worsened the symptoms, and whether there are any improvements.

Additional tests that the doctor may order include:

Blood Tests

Blood tests to rule out any other possible conditions may require a physician. This will help determine what caused the reaction and triggered the signs and symptoms.

Blood tests for detecting drug allergies are often only used when there’s a severe reaction to other tests like the skin test. This is because the blood tests for detecting allergic reactions are not as practical as the other tests.

Skin Tests

During skin tests, the doctor, allergist, or nurse does a negligible amount of drug administration to your skin using an injection patch or a tiny needle used to scratch it. A red, itchy, and raised bump will surface if there is a positive reaction.

Positive results show the presence of a drug allergy. However, the same can’t be said about a negative outcome. The determination is complicated based on the reliability of the tests. In some drugs, the negative result means there’s no allergic reaction, while in others, the interpretation doesn’t rule out the possibility of the condition.

Whichever the case, the result of a diagnostic workup through a thorough examination of the test results, the following conclusions can be derived:

  • A drug allergy is present
  • There is no drug allergy
  • You have a drug allergy, but with varying degrees of certainty

The conclusions help other doctors in making treatment decisions for future cases.

Treatment of Drug Allergy

Drug allergy treatment is divided into two categories

  1. Treating the current allergy symptoms
  2. Treatment that enables you to use allergy-causing drugs if it’s a medical necessity

While treating the present symptoms, the following are the interventions used:

Drug Withdrawal

If there is proof that you have a drug allergy through the doctor’s determination or the possibility of its presence, imperatively, you should stop taking the drug. It marks the first treatment method, which is the only necessary intervention in most cases.


Oral or injected corticosteroids may be used to treat severe allergic reaction symptoms, such as inflammations.


If necessary, the allergist, doctor, or nurse may give you a prescription of antihistamines or other over-the-counter antihistamines like Benadryl. The drug will block the activated chemicals by the immune system during an allergic reaction.

Treating Anaphylaxis

The most effective treatment of anaphylaxis is an immediate injection of epinephrine. Nevertheless, hospital care to maintain blood pressure and support breathing is equally mandatory.

While taking allergy-causing drugs for a confirmed case, the doctor will not prescribe any drug unless necessary.

If the condition is unconfirmed, there are two methods the doctor will use as an intervention. Both ways require careful supervision and supportive care services. The methods are:

a) Graded Challenge

The graded challenge drug administration involves four to five doses, beginning with a small amount before increasing to the maximum required dosage. If you still do not react to the dosage, the conclusion will be that you don’t have a drug allergy and will use the drug as directed.

b) Drug Desensitization

It involves using the drug from a small dosage to large doses at intervals of between 15 and 30 minutes over the day. If there is no reaction even after reaching the full dosage, the drug is safe.

How Can Drug Allergy Be Prevented?

If you have the condition:

  • Make the healthcare workers, such as the dentist or your pharmacist, aware of the reaction
  • Have emergency epinephrine with you all the time for severe cases of anaphylaxis
  • Wear a medical alert bracelet specific to your type of drug reaction

Bottom Line

If you experience any signs of a drug allergy or any significant adverse effects from your medicine, contact your doctor immediately.

If you know you’re allergic to a medicine, inform all of your medical professionals. This includes your dentist and any other medical professional who may prescribe medication.

Also, consider carrying a card identifying your medication allergy or wearing a bracelet or necklace identifying your drug allergy. This knowledge might save your life in an emergency.

And remember, any inquiries you have concerning your allergy should be sent to your doctor.

These might include:

  • What type of allergic response might I expect if I use this medication?
  • Is there anything else I should avoid because of my allergy?
  • Should I have any drugs on hand in case of an allergic reaction?
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