Question: What tests are used to determine if I have a drug allergy?
Answer: 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.
That having been said, however, there are some laboratory tests that can be helpful and for our major drug allergy group -- for the penicillin and related antibiotics -- we have very useful allergy skin tests that can be used to determine which patients remain sensitive after having a reaction in the past. So this type of skin testing may be helpful for penicillin and penicillin-family antibiotics to assess the current state of sensitivity.
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.
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