Overview
What is a drug allergy?
A drug allergy is an adverse drug reaction with a proven immunological cause.
What is a cutaneous adverse drug reaction (CADR)?
It is a skin or mucosal reaction that occurs as a result of an unintended response to a drug. It can be an immune or non-immune-mediated reaction.
A maculopapular drug exanthema is the most common type of CADR.
Causes
Many types of medications can cause maculopapular exanthema. Viral infections can sometimes cause a similar pattern of skin rash.
It appears as red spots, patches and bumps on the skin, usually on the trunk and limbs. The rash may be itchy, and typically starts few days to 2 weeks after the ingestion of the incriminating medication.
Prevention
What is a drug provocation test?
A drug provocation test is the controlled administration of a drug to diagnose an immune-mediated and non–immune-mediated drug reaction. It is usually done under medical supervision. Drug provocation test has the potential risk of inducing a more severe and uncontrollable relapse of the original reaction. It is therefore a test which should be reserved for specific situations and when the benefits outweigh the risks.
Detection & Treatment
Evaluating drug allergies/ cutaneous adverse drug reactions can be challenging. An accurate, detailed history and clinical examination will help to establish the type of CADR and to identify the culprit drug. Blood tests, skin biopsies and skin tests (eg. Skin prick tests, intradermal tests and patch tests) are sometimes needed in the evaluation, but the usefulness of these tests is dependent on the type of the reaction and the drugs involved.
Not all cases of drug allergies/ cutaneous adverse drug reactions require specific drug allergy testing and not every medication or type of CADR has a blood test or skin test to help in the diagnosis.
Treatment of maculopapular drug exanthema involves cessation of the culprit drug, with or without topical or systemic steroids and antihistamines. A maculopapular exanthema may herald a more serious cutaneous adverse drug reaction.
Care Management
After a drug allergy or hypersensitivity has been diagnosed, what should you do?
It is important to remember the drug(s) which you are allergic to and always inform your doctors about it. A wallet-size card stating the name of the drug and the reaction you had would be most useful in case of emergency. Avoidance of drugs which are you are allergic to will prevent unnecessary morbidity or mortality.
Drug allergies are captured on the electronic medical records that link many hospitals and clinics.
Specialties & Services
