Drug allergy – Symptoms, causes & treatment

Introduction

This blog attempts to present the hidden allergies when medications become adversaries. An untoward reaction after taking any medicine is referred to as a drug allergy.¹ Clinical classification of drug allergies is an immediate reaction (this type of drug allergy is visible after 1-6 hours of taking the drug) and non-immediate reactions (these reactions appear more than one hour after taking the drug).² Understanding the underlying causes of drug allergies is important to identify and manage these reactions effectively. If you suspect a drug allergy, seeking medical attention is crucial for proper diagnosis and treatment.  

Signs and Symptoms of Drug Allergy

If anyone is experiencing the below-listed symptoms then they might be experiencing drug allergies. Drug allergies can be experienced immediately after ingesting the drug or even after several hours of taking the drug. 

• Mild symptoms of drug allergy: 
• Skin rash
• hives
• wheezing 
• skin and eyes itching 
• lips, tongue, face swells up.³  
• Serious symptoms of drug allergy: 
• Anaphylaxis⁴
• skin turns blue 
• low blood pressure 
• breathing becomes difficult
• light-headedness
• losing consciousness.¹ 

When to See the Doctor

Some of the symptoms of a drug allergy can be life-threatening and require urgent medical care.¹

• If you experience a severe allergic reaction to a drug, an allergist (immunologist) possesses specialized expertise in diagnosing the issue and assisting you in creating a plan to ensure your future protection.
• If you experience breathing difficulties or other signs of severe asthma or anaphylaxis, visit the emergency facility, or use the local emergency number. 
• Make sure to maintain a record of all the medications you are presently using, and pay extra attention if you have experienced previous reactions to specific drugs. Share this list with your doctor and have a conversation about whether there are any specific medications you should avoid.¹²

Causes of Drug Allergy

The exact cause of drug allergies is not fully understood, but there are several factors that can contribute to their development. Here are some potential causes:

1. Patient-related causative factors: 

• Age: The occurrence of drug allergies can vary depending on age and gender. Allergic reactions to drugs are likely less common in children, possibly due to their immune system being less mature and lower overall drug intake.
  • However, in elderly patients, the prevalence of drug allergies can increase up to 30%, and they tend to be more severe. 
  • This could be attributed to the presence of other medical conditions (comorbidities) and the use of multiple medications concurrently.²
• Immune system response: Drug allergies occur when the immune system mistakenly identifies a drug as harmful and produces an allergic reaction. The immune system may produce specific antibodies called immunoglobulin E (IgE) in response to the drug.⁴
• Previous exposure: Prior exposure to a drug can sensitize the immune system and increase the risk of developing an allergic reaction upon subsequent exposure. This is known as a hypersensitivity reaction.^2,3
• Genetic factor: Some people may have a genetic predisposition to developing drug allergies. Genes play an important role in drug allergy.^2,5

2. Drug-related causative factors:

Following list of medicines that are commonly observed as a triggering cause of drug allergies. 

• Penicillin and other antibiotics like penicillin are the most frequent causes of drug allergies.¹
• Sulfa drugs
• Non-steroidal drugs
• Chemotherapy medicines¹
• X-ray contrast dye³
• Drugs used in treating seizures³
• Insulin derived from animal source³

Diagnosis of Drug Allergy

A physician thoroughly examines the patient’s medical history and symptoms in order to identify drug allergies.¹

• Medical history identifies previous and current drug use, toxicity, and allergenicity with previously and currently used drugs.⁶
• Allergy blood test / Allergen-specific Ig E levels: Ig E (immunoglobulin E) are antibodies found in high levels in the blood when a person is facing allergic reactions.⁷ They are detected using a radioimmunoassay test.²
• Lymphocyte transformation test (LTT):  This test will help identify T-cell-mediated delayed hypersensitivity.²
• Skin test: Skin tests can be helpful in identifying allergies that are caused by antibodies. These tests involve placing small amounts of allergic substances on your skin and observing any reaction.
• Patch test: It is useful in determining eczema reaction which might have got elicited due to topical application of the medicine.⁶
• Skin biopsy: A skin biopsy may not be helpful in determining whether a patient has a drug allergy. It might be helpful, nevertheless, if other skin disorders with typical histologic features are part of the differential diagnosis.²
• Drug provocation/challenge test: This test will steadily administer the drug in increasing order at regular interval of time, the purpose is to reproduce the symptoms that the patient experienced the first time. ²

Treatment of Drug Allergy

Relieving symptoms and preventing a serious reaction are the two main objectives of treatment.³

• Discontinuation of the medication: The first step in managing a drug allergy is to stop taking the offending medication immediately. This helps prevent further exposure and worsening of the allergic reaction.⁸
• Antihistamine medicines can help in relieving mild symptoms of drug allergy.
• Dilators of bronchioles help in reducing symptoms of wheezing.³
• Adrenaline is typically given for more severe anaphylactic symptoms (life-threatening reactions, difficulty breathing, or loss of consciousness).¹

Prevention of Drug Allergy

A medication allergy can typically not be avoided. 

• The easiest strategy to avoid an adverse response if you are known to have a drug allergy is to avoid taking that medication. 
• The use of similar medications is also to be avoided.³ If drug allergy symptoms aggravate immediately rush to the doctor.⁹
• Research has demonstrated that administering corticosteroids and antihistamines prior to the administration of x-ray contrast dye can effectively prevent allergic reactions in individuals who require such procedures.³
• Make sure to inform your doctor if you have any negative reactions while taking medication.
• Keep a record of all the medications you are currently taking and make a note of any past reactions you may have had to specific medications. It is important to share this information with your doctor to ensure your safety and well-being.¹²

Complications of Drug Allergy

An allergic trigger can cause anaphylaxis, a severe and perhaps fatal reaction. Anaphylaxis occurs when the immune system, which is the body’s natural defense mechanism, overreacts to a particular stimulus, which is not necessarily always an allergen. 

Some common triggers for anaphylaxis include:

• Certain foods like nuts, milk, fish, shellfish, eggs, and fruits, 
• certain medications such as antibiotics and non-steroidal anti-inflammatory drugs like aspirin
• general anesthesia
• contrast agents used in medical tests
• Insect stings, latex found in rubber gloves and condoms can also trigger anaphylaxis. 

Sometimes, there is no obvious trigger for anaphylaxis, and this is referred to as idiopathic anaphylaxis.¹⁰

Conclusion

In conclusion, it is essential to be aware of the potential risks and symptoms associated with drug allergies. By recognizing the signs, seeking prompt medical attention, and communicating effectively with healthcare professionals, individuals can better protect themselves from adverse reactions. Remember, knowledge is power when it comes to managing drug allergies and taking proactive steps can lead to safer and more effective medication use. Stay informed, stay vigilant, and prioritize your health and well-being.¹¹

Frequently Asked Questions (FAQs)

References:

1. Drug Allergy: Symptoms, Diagnosis & Treatments [Internet]. Available from: https://my.clevelandclinic.org/health/diseases/8621-medication-allergies
2. Drug allergies: MedlinePlus Medical Encyclopedia [Internet]. Available from: https://medlineplus.gov/ency/article/000819.htm
3. Drug Allergy | AAFA.org [Internet]. Available from: https://aafa.org/allergies/types-of-allergies/medicine-drug-allergy/ 
4. [Genetic predispositions in drug allergy: the role of HLA] – PubMed [Internet]. Available from: https://pubmed.ncbi.nlm.nih.gov/24834645/
5. Drug allergy: an updated practice parameter – PubMed [Internet]. Available from: https://pubmed.ncbi.nlm.nih.gov/20934625/
6. Allergy Blood Test: MedlinePlus Medical Test [Internet]. Available from: https://medlineplus.gov/lab-tests/allergy-blood-test/
7. Yazicioǧlu M. Approach to drug allergies in the childhood. Turkish Archives of Pediatrics/Türk Pediatri Arşivi [Internet]. 2014;49(2):99. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4462278/ 
8. Drug Allergies | Reactions, Symptoms & Treatment | ACAAI Public Website [Internet]. Available from: https://acaai.org/allergies/allergic-conditions/drug-allergies/
9. Anaphylaxis – NHS [Internet]. Available from: https://www.nhs.uk/conditions/anaphylaxis/
10. Medical error reduction and prevention – statpearls – NCBI bookshelf [Internet]. Medical Error Reduction and Prevention. 2022 [cited 2023 May 19]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499956/ 
11. Medications and drug allergic reactions [Internet]. American Academy of Allergy Asthma & Immunology. 2020 [cited 2023 May 19]. Available from: https://www.aaaai.org/tools-for-the-public/conditions-library/allergies/medications-and-drug-allergic-reactions 

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