The tuberculosis (TB) skin test is used to determine if you have ever been exposed to the bacterium that causes TB. The test involves injecting a small amount of TB protein under the skin of your inner forearm. TB is an infectious disease that mainly affects the lungs and can potentially lead to serious complications. The test can be used as part of the diagnosis for the disease.
There are many reasons why this test is usually done, including the following:
- you have been in close contact with a TB-infected person
- you have traveled to a foreign country that has a high incidence of TB
- you are a health care worker
- your employer or school requests that you have this test performed prior to your start date
Risks and precautions
The TB skin test is usually straightforward and safe. However, there are some risks of side effects, including severe redness, swelling, and pain in the arm, particularly in people who have had a positive skin test before. Get immediate medical assistance if you experience any of these side effects.
It is important that you understand all the risks of complications and side effects of the test, and what you or your doctor can do to avoid them. Make sure that your doctor is aware of all your concerns.
Before the test
No preparation is necessary for this test. If you have had TB or a positive TB skin test before, inform your doctor or health care professional. It is also important to tell your doctor if you have or have had any of the following:
- major viral infection (e.g., HIV, mumps) - this does not include the common cold
- current or previous TB infection
- large burns or eczema on the test site
- a measles vaccination within the last 4 weeks
- previous adverse reactions to TB tests or vaccinations
If you are taking any prescription or over-the-counter (non-prescription) medications, supplements, or herbal products, make sure you inform your doctor or pharmacist. Ask them whether it is necessary for you to stop taking any of these medications and products before the test. It is also important to tell them if you have allergies to certain medications or have certain medical conditions.