Allergic reactions occur as an immune response of our body to a foreign substance. When the allergic reaction is due to a drug, new or old, it is said to be a drug allergy. Adverse drug reactions can occur with any class of drugs, but more so in case of antibiotics followed by anti-tumor drugs.
Symptoms of drug allergy
Symptoms of drug allergy are the same for any type of allergy. Common ones are skin rash, hives, and itching of the skin or eyes. These are not very serious symptoms. These reactions are usually treated by substituting the current drug with another.
However, severe reactions after taking the medication include swelling or tightening of the airways, dizziness or lightheadedness, rapid pulse, or even loss of consciousness. Seek emergency treatment since these are anaphylactic symptoms that are potentially life threatening.
Who can get drug allergy
Anyone and everyone can be allergic to one or the other drug. Generally children and middle aged people are more prone to drug allergy than others. Female gender is also a risk factor for allergic reactions to a drug. You may also have an allergic reaction if
Common drug allergies
You can have an allergic reaction to any drug. But some are more common than others. Here's a list of the most common drug allergies.
How to identify a drug allergy
It is very difficult to identify a drug allergy. And that is because there are very few good laboratory tests that can be helpful in diagnosing them. What happens is, generally the original form of medication does not cause the allergic reaction. It is the modified form of the drug or the metabolite of the drug that the immune system responds to. However, the skin test for penicillin is very effective because all of the important metabolites of penicillin have been identified. So much so, the test can correctly identify not only who is allergic to penicillin but also who is not allergic. There are a few tests to diagnose drug allergy and these include
Blood test Allergy to some antibiotics, muscle relaxants and insulin can be diagnosed through blood test.
Skin test Skin test may be required for certain antibiotics. A small amount of the drug is injected into the skin. If you're allergic to the drug being tested, you will develop a reaction.
Drug provocation test This test is resorted to when the other two tests are inconclusive. In this test, you will be given gradually increasing doses of the offending drug. If there is a reaction, sensitivity to the drug is indicated; if not, then it could be considered a safe treatment option.
Since lab tests or skin tests are not always helpful, allergists have to depend on a detailed and accurate history of all your current and past medication to identify which drug is responsible.
'First of all, the most important test of a drug allergy is not a laboratory test or a skin test at all, but a careful history of what happened when the allergic reaction occurred previously. That tells an allergist, more than any testing that is done, whether or not the drug reaction was due to an allergic mechanism, allergic cause, and also gives some estimate of whether or not that type of allergy is likely to persist over time. So a good careful history is the most important tool that we have to determine who is allergic to a particular drug', says N. Franklin Adkinson, M.D., Prof., Div. of Allergy and Clinical Immunology, Johns Hopkins University. 'For many other drugs, including other antibiotics, we don't have a validated skin test, and we have to rely on that crucial historical information to tell us, to give us an assessment of how likely it is that a drug allergy exists'.
Practical tips
Reference:
https://www.ncbi.nlm.nih.gov/pubmed/12592301
https://www.mayoclinic.org/diseases-conditions/drug-allergy/symptoms-causes/syc-20371835
http://aacijournal.biomedcentral.com/articles/10.1186/1710-1492-7-S1-S10
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