drug allergy

Photo via Mayo Clinic

What is a Drug Allergy?

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

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

Drug allergies are rather annoying and serious, on rare occasions, anaphylaxis, which is a severe condition that affects multiple body parts, and loss of consciousness may occur. Other life threatening responses to medication includes 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 Some Drug Allergy Symptoms?

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:

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  1. Hives
  2. Fever
  3. Itching
  4. Wheezing
  5. Skin rashes
  6. Short breaths
  7. Running nose
  8. Watery and itchy eyes
  9. Swelling of the face, lips and or tongues
  10. Anaphylaxis is a severe drug allergy needs to be treated immediately

Is Anaphylaxis Drug Allergy Life-Threatening?

Yes, this rare but severe drug allergy can be fatal if left untreated. Typically an anaphylaxis drug reaction will require a quick trip to the emergency room followed by a prompt shot of epinephrine (adrenaline).

The signs and symptoms of anaphylaxis include:

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

Apart from sickness serum, which occasionally affects the joints causing pain as well as fever, swelling, rash, and nausea, the following are other conditions 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 among other symptoms.
  3. Drug rash with Eosinophilia & Systematic Symptoms (DRESS) – Causes rash, high counts of white blood cells, swelling, hepatitis infection recurrence.

What Causes Drug Allergies?

The development of drug allergies occurs when the sensitivity of your immune system extends to identifying drugs as harmful. What this means is that 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 flags it and initiates an attack on the particle through the immune system. During the process, the chemicals released causes the symptoms associated with the drug allergy.

Sometimes, the 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.

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

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

The symptoms of drug allergy 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 response to a drug, which produces signs and symptoms akin to drug allergy, but not caused by the immune system activity.

Which Drugs Cause the Most Drug Allergies?

  • Local anesthetics
  • Imaging tests dyes
  • Pain management opiates
  • Paclitaxeldocetaxel, and procarbazine
  • Anticonvulsants like lamotrigine and carbamazepine
  • Chemotherapy medications like docetaxel, paclitaxel and procarbazine
  • Aspirin, ibuprofen and other nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Monoclonal antibody therapy drugs like ibritumomab tiuxetan and trastuzumab
  • Antibiotics like penicillin and sulfa antibiotics like sulfamethoxazole trimethoprim

What are the Risk Factors of Drug Allergy?

There are several factors that increase the risks of drug allergy. Some of them include:

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

Drug Allergy Diagnosis

Accurate diagnosis of drug allergy results from thorough and appropriate examination. In some cases, drug allergies are over diagnosed, which leads to patients reporting cases that have never been confirmed. A misdiagnosis of drug allergy often results in the use of inappropriate and possibly expensive drugs.

During a diagnosis, the doctor will ask you questions 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.

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Additional tests that may be ordered by the doctor include:

Blood Tests

Blood tests, to rule out any other possible conditions, may be required by a physician. This will help in determining what exactly caused the reaction and triggered the signs and symptoms. The blood tests for the detection of drug allergy 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 effective as the other tests.

Skin tests

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

Positive results show the presence of a drug allergy. The same can’t be said about a negative result. The determination is difficult 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 thorough examination of the test results, the following conclusions can be derived:

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  • You suffer from a drug allergy
  • You don’t suffer from a 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.

How Is a Drug Allergy Treated?

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:

Corticosteroids

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

Antihistamines

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.

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Drug Withdrawal

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

Treating Anaphylaxis

The most effective treatment of anaphylaxis is an immediate injection of epinephrine. Hospital care to keep blood pressure maintained and to support breathing is equally mandatory.

While taking allergy causing drugs for a confirmed case, the doctor will not prescribe any drug unless absolutely necessary. If the condition is unconfirmed, there are two methods the doctor will use as an intervention. Both methods require careful supervision and supportive care services.

The methods are:

Graded Challenge

The graded challenge drug administration involves four to five doses, beginning with a small dose before increasing to the maximum required dosage. If after the dosage you still have no reaction, the conclusion will be that you don’t have a drug allergy and you will be able to use the drug as directed.

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Drug Desensitization

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

How Can Drug Allergies Be Prevented?

If you have the condition:

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

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