A skin test is given to individuals to determine if they have ever been exposed to tuberculosis (TB). The test is called a tuberculin skin test. The Mantoux tuberculin skin test is the standard way of determining if an individual is infected with TB. Occasionally, the individual who has received the skin test has an allergic reaction.
How Test is Given
The Mantoux test requires a small amount of TB antigens to be injected into the top layer of skin in the forearm. If the test is positive, your skin will react within a few days by forming a red bump where the TB antigens were inserted. If the test is negative, there your skin will not react in the spot where the TB antigens were inserted.
The test seems simple enough and all goes well if the body does not have an allergic reaction. The body has an allergic reaction to the TB test when it identifies the Mantoux test as something harmful to the body. An allergic reaction can include a rash on the tested area, swelling and pain, or a sore in the area where the test was administered.
Problems with Allergic Reactions
Having an allergic reaction to a TB test can lead a health care professional to think you tested positive to TB. Health care professionals can assume you have TB since a bump on the site is the indicator they look for to determine if a test is positive. If it is determined you are allergic to TB testing, you should remember and inform all health care professionals in the future who desire to test you as reactions get severe after repeated exposures. A reaction can range from a simple rash to anaphylaxis.
If You Appear to Have TB
An allergic reaction makes it seems that the individual has TB. To take precautionary measures, health care professionals will order additional tests to be sure that a person is in fact not infected with TB. These additional tests include blood tests and X-rays. Once they come back and prove to be negative, the health care professional can determine if you are in fact just allergic to the TB antigens.
Alternative to TB Test
There is a new test that has only been used since 2009 that may prove to be best for those allergic to the common TB test. The new test only requires a single office visit and is not affected by previous vaccinations. QuantiFERON-TB Gold test is the name of the new test; it requires a blood sample and provides greater accuracy than the typical TB test.