Allergy TB Skin Test

What is An Allergy TB Skin Test?

When investigating for tuberculosis, the most commonly used method is the Mantoux test. It is also called the Tuberculin Sensitivity test and the PDD or Purified Protein Derivative test. This test resembles an allergy TB skin test in the way it is done and is the standard test for this disease. This procedure is done by injecting the TB antigen under the skin. 

In the United States, the amount of antigen used is one tenth of a millimeter and is injected under the skin. The reaction is then read about forty eight hours later, though sometimes a second time at seventy two hours. The outcome of the test is read by measuring the size of the bump on the arm. If there is no reaction, there is nothing to worry about. But if there is a reaction, action will be taken based on whether it is five, ten or fifteen millimeters as well as the health of the patient. The standard approach is to take action if the reaction is ten or more millimeters in size and the patient has been in contact with someone who is known to have infectious tuberculosis, was recently in a country where tuberculosis is prevalent or for some reason the patient travels regularly in countries where there is the chance of exposure.

The test is referred to as an allergy TB skin test because of how closely it resembles a regular allergy test.  Just like with allergy tests the reaction to that which is injected is what tells the health care provide if there is an illness or if there is nothing to be concerned about.