However, there are times when a skin test should not be done.

It takes 48 to 72 hours to read the skin test.

"It can take, in fact, 8 to 12 weeks for a skin test to turn positive after someone has been exposed," he said.

Do that same people are allergic to the color a skin test is necessary.

All prisoners now receive at least a skin test for the disease.

They said both her skin test and chest X-ray were clear.

The 21 other crew members had not taken skin tests before flying with her.

This is because their immune systems often do not work well enough to respond to a skin test.

A skin test performed earlier in the year showed that she was not infected.

If this doesn't tell your doctor whether you have a drug allergy, then he or she may do skin tests.