Tests and diagnosis

By Mayo Clinic Staff

If you have an unexpected drug reaction, steps that your doctor may take to diagnose the source of the problem include:

  • A physical examination. In addition to a physical exam, your doctor will have a number of questions. For example, he or she might ask how long after you took the medication you began having symptoms.
  • Blood tests. A blood sample can only be used to detect an allergy to a few drugs, such as certain antibiotics, muscle relaxants and insulin. Skin tests are generally preferred because they're more accurate in detecting drug allergy, but blood tests may be used when someone has had a severe reaction in the past, because skin testing could cause another such reaction.
  • Skin tests. For some drugs, including certain antibiotics, an allergy skin test may be used to determine whether you're allergic. A small amount of the drug is injected into the skin of your forearm or back. If you're allergic to the drug being tested, you develop a red, raised bump or other reaction.
  • Drug provocation tests. During drug provocation testing, gradually increasing doses of the offending drug are given. The drug can be given in different ways for the test, including orally or under the skin. A reaction indicates a possible allergy or sensitivity to the drug. If reactions to the drug are mild or there's no evidence of an allergic reaction, the drug may be a safe treatment choice. This test is usually used only when an alternative drug won't work as well or isn't an option. It may also be used when skin and blood tests aren't conclusive. Risks include a severe reaction and possibly anaphylaxis. Generally, only specialized allergy centers perform provocation tests for drug allergy.
Oct. 14, 2011

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