TB is on the rise, especially with the mass imigration from mexico.

You must be applying for a job in the health field? it is required.

I have had a few TB test with no ill effects,

Heres some info from Rutgers University
http://health.rutgers.edu/Immunizations/TB.htm

PPD Tuberculosis Skin Test

The PPD is an antigen - a substance that stimulates the immune system to eliminate or fight foreign substances in the body. PPD is taken from dead tuberculosis bacteria.
During the Mantoux / PPD Tuberculosis skin test, 0.1 ml of purified protein derivative (PPD) containing 5 tuberculin units is drawn into a 27-gauge syringe.

PPD tuberculosis skin test is administered into the epidermis (top layer of skin) of the inner forearm. The nurse fills a syringe with purified protein derivative (PPD), and injects the needle, beveled side up, into the forearm. The PPD is released into the forearm as the nurse depresses the plunger of the syringe. As the PPD is released, a raised bump forms just under the skin's surface.

The nurse should make two pen marks on either side of the bump to indicate where the injection was performed on the forearm. Then, he or she will record the date, time and forearm where the tuberculin was injected.

After the Mantoux / PPD tuberculosis skin test is administered, it is important that you do not touch, scratch, rub or press on the test site. Any manipluation of the test site could alter the test.

You may continue with your daily personal hygiene activities, but you should avoid using ointments, lotions, and sunscreens until your healthcare provider has examined the test site.

Since Mycobacteria tuberculosis, the bacteria that causes tuberculosis infection/disease, produces a delayed hypersensitivity reaction, the results of the Mantoux / PDD tuberculosis test can not be read until 48 to 72 hours after the testing.

The reading of the test results must be performed by a healthcare professional. It is very important to return to your healthcare provider to have your forearm examined even if your forearm does not appear to be infected.

Forty-eight to 72 hours after the Mantoux / PPD tuberculosis skin test is performed, you will need to return to your healthcare provider to have the results read. This involves a brief examination of the test site.

A nurse will look at the test site and palpate the area to determine if the test site is raised and feels hard to the touch. He or she will use a ruler to measure the raised bump, if one exists. The nurse will record the results in millimeters to represent the size of the raised bump. If the test site does not have a raised bump, "0 mm" will be recorded.

Mantoux / PPD tuberculosis skin test results showing a raised bump measuring 5 mm or greater is interpreted as a positive result