Publication Number 301232 CS 339493-B August 07, 2023

What You Need to Know About the TB Skin Test

Getting tested and treated for tuberculosis (TB)

can protect yourself, your family and friends, 

and your community. There are two types 

of tests for TB infection: the TB blood test 

and the TB skin test. This fact sheet provides 

information on the TB skin test. 

TB germs spread through 

the air from one person to 

another. Anyone can get TB. 

TB germs usually attack the 

lungs but can move to any 

part of your body. 

The bacteria responsible 

for causing TB can live in 

the body for years without 

symptoms. This is called 

latent TB infection or inactive 

TB. People with inactive 

TB do not have signs and 

symptoms of active TB 

disease and cannot spread 

TB bacteria to others. 

Without treatment, inactive 

TB can become active TB 

disease at any time and 

make you sick. If not treated 

properly, active TB disease 

can be fatal.

Tuberculosis 

Bacteria

TB Skin Test

The TB skin test, also known as the tuberculin skin 

test, may be used to find out if you are infected 

with TB germs. A health care worker will use a small 

needle to inject testing fluid (called tuberculin) under 

the skin on the lower part of your inner arm.

After Receiving the TB Skin Test

After the test, you should avoid using bandages, 

putting on lotion, or scratching the test area 

because it may affect the results. You can wash 

the area with water, but do not wipe or scrub. If 

the area itches, put an ice cube or cold cloth on it. 

After 2 or 3 days, you must return to have a health care worker 

read your skin test. You may have swelling or a bump where the 

testing fluid was injected. The health care worker will measure the 

bump or swelling and will tell you if your skin test reaction is 

positive or negative. 

If you are not able to return within 2 to 3 days, you will need 

to repeat the skin test again.

Return to have your skin test read

Date: 

Time: 

Location: 
If your skin test is POSITIVE:

• You have TB germs in your body. 

• The test does not tell whether you have 

inactive TB or active TB disease. You 

will need other tests, such as a physical 

examination, chest x-ray, and lab work to 

determine if you have active TB disease.

• Once you test positive for TB, you will 

always have a positive skin test even if 

you complete treatment for TB. Ask your 

health care provider for a written record of 

your positive TB skin test result. This will be 

helpful if you are asked to have another test 

in the future.

If your TB skin test is NEGATIVE:

• Your body did not react to the test. You likely 

do not have inactive TB or active TB disease. 

• You may need to have more tests if:

» You have symptoms of active TB 

disease, like coughing, chest pain, 

fever, weight loss, or tiredness. 

» You have HIV infection. 

» Your exposure to TB germs was recent. 

You may need a second skin test 8 to 10 

weeks after the last time you spent time 

with someone with active TB disease. This 

is because it can take several weeks after 

infection for your immune system to react 

to the TB skin test. If your reaction to the 

second test is negative, you likely do not 

have inactive TB or active TB disease.

Did You Receive the Bacille Calmette-Guérin (BCG) Vaccine?

BCG is a vaccine for TB. This vaccine is not widely used in the United States. 

Many people born outside of the United States have received the BCG TB vaccine. 

It is often given to infants and small children in other countries where TB is more 

common. It protects children in those countries from getting severe forms of active 

TB disease, such as TB meningitis. Protection from TB goes away as people get older. 

Let your health care provider know if you were previously vaccinated 

with the BCG TB vaccine. 

In some people, the BCG TB vaccine may cause a positive TB skin test even if they are not infected with TB 

germs. Unlike the TB skin test, TB blood tests are not affected by prior BCG vaccination. Therefore, TB blood 

tests are the preferred test for people who have received the BCG TB vaccine.

TB Can Be Treated

If you have inactive TB, you can take medicine to prevent the development 

of active TB disease even if you do not feel sick. 

TB germs can live in your body for years without causing symptoms. Without 

treatment, inactive TB can develop into active TB disease and make you sick.

If you have been diagnosed with active TB disease, you will need to take and 

finish all your TB medicine. This is to help you feel better and prevent other 

people from getting sick.