Your doctor will diagnose a
drug allergy by asking you questions about the
medicines you are or have recently been taking, your past health, and your
symptoms (medical history) and by doing a physical exam. To find
out which medicine is causing your allergic reaction, your doctor will
- Your medicine. Some medicines are more likely to cause an
allergic reaction than others.
- Whether you have a
drug allergy or another adverse reaction to medication. You have more
treatment options if you have an adverse reaction that does not involve the
- How many medicines you are taking. If you take
several medicines, the medicine you began taking most recently is often the
Your doctor probably will ask you to stop taking the
medicine that is most likely to be causing the reaction. If this does not help,
your doctor may ask you to stop taking other medicines, until you can find
which medicine is causing the allergic reaction.
If your doctor
cannot find out which medicine is causing the reaction, he or she may suggest a
skin test. In a skin test, your doctor will place a
small amount of medicine on or under your skin to see if your body reacts to
it. But a skin test does not work for all medicines, and you risk having a
Skin tests can diagnose allergies to:
- Penicillin, which is the most common
cause of drug allergies.
- Heterologous serum (used in the
prevention or treatment of
gangrene, organ transplant rejection, and snake and
- Streptokinase (used to dissolve blood
- Chymopapain (used for
Another way to find the cause of your allergic reaction is
a medicine challenge. In a medicine challenge, you start by taking small doses
of a medicine and slowly increase how much you take to see whether you have an
allergic reaction. This challenge is usually done where emergency medical help
is available and under the supervision of a health professional.
If you have medicine fever, serum sickness, or other complications, you
may need more tests. These tests include a chest
X-ray and blood tests to see how well your liver and
kidneys are working.