Infrequently, medications used to treat a medical problem will cause another problem- an allergic reaction. There are a number of ways that drug allergy can present.
The type of an allergic reaction can be classified based on how the reaction occurs. This system of classification is important because some of the reactions may be life threatening with re-exposure to the medications.
Type One Reactions - frequently an immediate reaction
- Anaphylactic shock
- Urticaria or hives
- Angioedema or swelling
Type Two Reactions - rare
Type Three Reactions
- Serum Sickness - hives, fever, joint pain, and swollen glands
Type Four Reactions
- Contact dermatitis - a poison ivy-like rash
This is done clinically. A health care professional should see the patient and try to sort out what is going on. This is very important for a number of reasons. First, as more and more reactions occur, the list of medications that can be used becomes less and less. Secondly, more expensive medications may be required. Third, the next exposure may cause a serious reaction. Fourth, there are very few tests available for reactions to medications. When the medication is needed, long desensitization procedures may be necessary.
The health care provider can help determine the type of rash. Many times in children it is a virus or an interaction between the drug and the "bug" that causes the skin reaction. The skin reactions that are of concern would be urticaria or hives. Recall, a hive is a raised area of skin that is itchy and usually does not stay in the same spot for more than a day. If there are sores in the mouth, this is of concern and it is important for the health care professional to know about it.
The allergist has a few tools to help with the diagnosis. The most important tool is the medical history and the physical examination. There are very few special tests available. Up until recently we were unable to obtain two products that were used in penicillin skin testing. These are now available and are being used to diagnosis allergy to penicillin and medications related to penicillin. Drug testing can be performed for penicillin, local anesthetics, and insulins. The limited availability of test materials forces the allergist to do challenge or desensitization procedures. These a only done if there are no other choices of medication to treat the specific problem.
Remember, the story and the examination are the most important pieces needed to make the diagnosis of medication allergy.
One to two million people in this country experience a reaction to a medication each year. These reactions usually involve the skin.
Of all hospitalizations each year, 2-5% are due to adverse reactions to a medication.
Antibiotics are the most common agents causing adverse reactions.
Treatment of Medication Reactions
At the time of the reaction, your doctor will offer supportive care depending on the nature of the reaction. Discontinuation of the medication is the first step when possible. A substitute medication may be an alternative.
Challenges and desensitization are available. In a challenge, large amounts of the suspected agent are given over time, carefully watching for any reactions. The desensitization is a slower more laborious process. After a successful desensitization, the medication must be used on a daily basis to maintain the desensitized condition.