Drug Allergy
What is a Drug Allergy?
Table of Contents
A drug allergy arises when the immune system reacts in an adverse way to a drug. This tends to cause typical symptoms of rashes, swelling, and potentially anaphylaxis. There are, however, many types of allergic responses that can occur.
Drug allergies are notoriously over diagnosed especially antibiotic allergies. Around 10% of the UK population report a penicillin allergy, and yet only 1% are likely to be truly allergic. It is vital to diagnose drug allergies correctly and failure to do so can result in increasingly complex drugs being used which are unnecessary and have the potential to cause more harm.
Many drugs cause side effects such as diarrhoea, abdominal pain, dry mouth etc but it is important to differentiate these from true allergic reactions.
Despite common belief, there is not an easy test for diagnosing a drug allergy. Many cases of drug allergy can be diagnosed (or undiagnosed) based on a clear allergy history. If there is any doubt, skin prick testing and intradermal testing to the drug may be carried out in specialised centres.
This involves pricking the skin with the drug involved (skin prick testing) or injecting a small amount of the drug under the skin (intradermal testing). If these tests are negative, then an oral drug challenge may be arranged where a test dose of the drug is given in a hospital setting.
Dr Helen can provide a clinical assessment of drug allergies as part of a general consultation about allergies but does not undertake specialist assessment. Please contact us if you would like more information.
Drug Allergy Explained
A drug allergy refers to an adverse reaction of the immune system to a medication. In the UK, like elsewhere, people can develop allergies to any type of drug, be it a prescription or over-the-counter remedy. While many drug reactions are a consequence of the drug’s side effects and not necessarily an allergic reaction, a genuine drug allergy is specifically caused by an immune response.
Drug Allergy Symptoms
The symptoms can range from mild to severe and can manifest in various ways. Some common symptoms include:
- Skin rashes, such as hives or a more widespread rash.
- Itching.
- Fever.
- Shortness of breath or wheezing.
- Runny nose.
- Swelling.
- Anaphylaxis, a severe and potentially life-threatening reaction, which may include difficulty in breathing, a rapid or irregular heartbeat, confusion, and a drop in blood pressure.
Drug Allergy Causes
An allergy occurs when the immune system mistakenly identifies a drug as a harmful substance, similar to the way it identifies pathogens like bacteria and viruses. This prompts the immune system to produce antibodies to fight the drug. Subsequent exposure to the drug may lead to a more rapid and intense allergic reaction, as the body is now “primed” to fight off what it perceives as an invader.
Common Drugs that Can Cause Allergies
In the UK, some drugs are more commonly associated with allergic reactions. These include:
- Penicillin and related antibiotics.
- Sulfa drugs.
- Antiseizure medications.
- Nonsteroidal anti-inflammatory drugs (NSAIDs), like aspirin and ibuprofen.
- Chemotherapy drugs.
Drug Allergy Symptoms
The symptoms can range from mild to severe and can manifest in various ways. Some common symptoms include:
- Skin rashes, such as hives or a more widespread rash.
- Itching.
- Fever.
- Shortness of breath or wheezing.
- Runny nose.
- Swelling.
- Anaphylaxis, a severe and potentially life-threatening reaction, which may include difficulty in breathing, a rapid or irregular heartbeat, confusion, and a drop in blood pressure.
Drug Allergy Causes
An allergy occurs when the immune system mistakenly identifies a drug as a harmful substance, similar to the way it identifies pathogens like bacteria and viruses. This prompts the immune system to produce antibodies to fight the drug. Subsequent exposure to the drug may lead to a more rapid and intense allergic reaction, as the body is now “primed” to fight off what it perceives as an invader.
Common Drugs that Can Cause Allergies
In the UK, some drugs are more commonly associated with allergic reactions. These include:
- Penicillin and other antibiotics
- Anaesthetics
- Antiseizure medications
- Nonsteroidal anti-inflammatory drugs (NSAIDs), like aspirin and ibuprofen
- Chemotherapy drugs
- Contrast drugs like iodine, used for some CT and MRI scans
Drug Allergy Diagnosis and Treatment
If someone suspects they have a an allergy to a drug, it is crucial to consult a healthcare professional. They will take a detailed history, including the onset of symptoms, the drug involved, and any previous drug reactions.
Skin tests, particularly for penicillin and some other drugs, can be conducted to confirm an allergy. However, for many medications, there isn’t a reliable skin test, and diagnosis is based largely on a detailed medical history and the symptoms presented.
Treatment for a drug allergic reaction can vary:
- Discontinuing the drug is the first step
- Antihistamines can be used to alleviate some symptoms like itching and rash
- For more severe reactions, corticosteroids may be prescribed
- Anaphylaxis requires immediate medical attention and treatment with adrenaline
Skin tests, can be conducted to confirm an allergy. However, for many medications, there isn’t a reliable skin test, and diagnosis is based largely on a detailed medical history and the symptoms presented.
Prevention and Management
If someone is diagnosed with an allergy to a drug they should inform all healthcare providers about this allergy and always read drug labels carefully. Wearing a medical alert bracelet can be lifesaving, especially if one has had a severe reaction in the past.
In conclusion, drug allergies are immune responses to medications that can result in a variety of symptoms, ranging from mild to severe. Proper diagnosis, management, and awareness are essential in ensuring the safety and well-being of individuals with these allergies.
For any allergy questions or issues that you may have, contact us as soon as you can so you can get the correct diagnosis and treatment
