Drug Allergy

Drug allergy occurs when the body’s immune system becomes overly sensitive to a harmless substance such as medication and induces an allergic reaction.

It is characterized by an abnormal reaction of the immune system that produces allergic reactions when some medications are taken into the body, producing rashes, sometimes fever, breathing difficulty, etc.

In severe cases, a drug allergy could result in anaphylaxis, which is a condition that affects the multiple body systems causing it to malfunction. It is usually life-threatening as it could lead to tightening of the airways and throat, nausea or abdominal cramps, dizziness, sometimes seizure, and loss of consciousness.

A drug reaction or side effect is different from a drug allergic reaction. All medications can produce potential side effects, but only about 5 to 10 % of these adverse drug reactions are allergic reactions. A drug side effect could be an overdose of medication.

Common Drug Allergy List

Some of the most common drug allergies include:

• Sulfa drugs; antibiotics containing sulfonamides.
• Penicillin
• Chemotherapy drugs; used for treating cancer.
• Anticonvulsant drugs
• Some medications for autoimmune diseases.
• Pain relievers.
• NSAIDs drugs such as ibuprofen, naproxen.
• Anticonvulsant drugs such as carbamazepine, lamotrigine, phenytoin etc.
• Muscle relaxants such as atracurium, succinylcholine, vecuronium, etc. [1].

Causes

A drug allergy is caused by the primary exposure to drugs that your body system may as a harmful substance which causes your immune system to develop antibodies to that drug, which produces allergic reactions. 

It could be that the immune system has produced some antibodies called immunoglobulin E (IgE) specific to the drug. The drug may bind to a certain type of immune system called the T cells, which produces a complex that releases chemicals that allergic reactions which could produce an effect in the nose, throat, ears, lining of the stomach, and the skin. 

Sometimes, it could take several exposures to the medication to develop the drug allergy. Hence you may not be aware of your exposure to the drug producing the effect.

Any drug could produce a drug allergy in different people although some drugs can produce more effect than others. 

Risk Factors of Drug Allergy

Anyone could have a drug reaction, but some factors cause the possibility of having a drug reaction occurs. They include:

• A medical history of other allergies such as hay fever, food allergy, etc.
• Family history of allergies
• Increased exposure to the drug due to increase in dosage, repetitive use, and prolonged use of the drug
• Certain autoimmune diseases or infections or certain diseases have common association with allergic drug reactions such as HIV EBV (Epstein Barr Virus).

Complications of Drug Allergy

Drug allergy can affect the functioning of your immune system and reduce its efficiency. Sometimes it could lead to life-threatening anaphylaxis as it affects multiple body functions.

Symptoms

Usually, that shows after a minimum of an hour after medications have been administered. Such reactions include:

• Skin rash
• Hives
• Itching and watery eyes
• Wheezing
• Shortness of breath
• Runny nose
• Swellings
• Irregular heartbeat

Some symptoms could develop after a while, they include:

• Serum sickness resulting in fever, pains in joints, rash, swelling, and nausea.
• Anemia caused by a reduction in blood cells due to the drug
• Inflammation of the nephritis in the kidney causing blood in the urine.
• Drug rash with eosinophilia and systemic symptoms increasing white blood cell count, swollen lymph nodes, etc.

Diagnosis of Drug Allergies

Diagnosing drug allergies could be pretty difficult. Some of the specific questions to ask the patient include: 

• What drug do you suspect caused your reaction?
• When did you start taking it, and have you stopped taking it?
• How long after drug administration did you notice symptoms, and what was your experience?
• What was the duration of your symptoms, and what did you do to relieve them?
• What are your other medications, both prescription and over-the-counter?
• Do you consume herbal medications or take vitamin or mineral supplements? Which ones?

A skin test may be carried out (accurate only for penicillin). This procedure involves administering a small amount of suspected drug to the skin, either with a patch or a needle that scratches the skin. A positive reaction such as a red itchy rash indicates a drug allergy.

Other diagnostic procedures are :

• On physical examination, the doctor will examine for signs of allergic reactions.
• Drug challenge test.
• Blood tests help in diagnosing drug allergies.
• Skin patch testing and delayed intradermal tests can diagnose severe allergic reactions [2] [3].

Treatment of Drug Allergy

Drug allergy cannot be treated but can be managed. The management of the condition and its symptoms can be achieved by:

• Changing the drug causing the allergy to reduce exposure to the drug.
• Your doctor may prescribe other medications to help control the symptoms. They include drugs such as an antihistamine. 

The immune system produces histamine when it recognizes a foreign substance in the body, leading to allergic reactions such as swelling, itching, and irritation. An antihistamine will reduce the production of histamine and stop allergic symptoms.

• Medications such as corticosteroids could also help relieve drug reaction symptoms by reducing inflammations.
• The use of Bronchodilators to open the airways in the case of wheezing and difficult breathing. It helps make breathing easy.
• The patient might need to undergo drug desensitization if there are no suitable alternate antibiotics. This procedure involves taking the drug in an increasing amount until the patient can tolerate the needed dose with reduced effect. The patient will closely be monitored during this period.
• In case of an anaphylaxis condition (the severe life-threatening reaction that can simultaneously affect two or more organ systems), the patient will be treated with epinephrine injections under close observation.

Prevention of Drug Allergy

The preventive measures include:

• Avoid exposure to the causative drug
• Inform your health care workers of your identified drug allergy
• If possible, wear a bracelet that indicates your drug allergy in case of an emergency to ensure proper treatment 

FAQ

• How long does it take to have an allergic reaction to a drug?

The duration of manifestation differs from person to person. It would take just a few minutes for some persons and several weeks of continuously taking the drug for some other person. However, it takes at least an hour before symptoms manifest in most cases.

• Are drug allergy symptoms different than other symptoms?

Drug allergy symptoms are just like symptoms of other allergies, which counts for the reading because it is quite challenging to diagnose. However, a combination of dizziness, vomiting, wheezing, running nose, itching, rash on the skin, and even anaphylaxis could indicate drug allergy.

• How long does a drug reaction last?

The body’s immune system produces histamine in response to recognizing foreign substances or allergens in the body. It may last as long as the effect of the histamine produced lasts. Sometimes it could last for 6weeks or more.

• Can a drug allergy go away?

For most mild drug allergies, symptoms may go away within a few days after the causative drug has been stopped. However, some drug allergies can be quite severe, and it takes time to heal after administering proper treatment.

• How do you get rid of drug allergy rash?

Drug allergy rash goes away after histamine’s action has been stopped and the drug causing the allergic effect stopped.

References

1. https://www.webmd.com/allergies/most-common-drugs-that-cause-allergiesBarbaud A, Collet E, Milpied B, et al. Toxidermies group of the French Society of Dermatology. A multicentre study to determine the value and safety of drug patch tests for the three main classes of severe adverse drug reactions. Br J Dermatol 2013;168:555–62. [PubMed] [Google Scholar]
2. 25. Torres MJ, Romano A, Celik G, et al. Approach to the diagnosis of drug hypersensitivity reactions: similarities and differences between Europe and North America. Clin Transl Allergy 2017;7:7.