Explanation

A sweat test is when your doctor collects some sweat from your skin (usually your forearm) and sends it to a laboratory. In the laboratory it will be tested for high levels of sodium chloride, which is another name for salt.

If you have cystic fibrosis (CF) , you have more salt in your sweat than people without the illness.

Why do I need one?

A sweat test is used to diagnose CF.

Your doctor might do a sweat test if someone in your family had CF, or someone has it now, or if you have any problems that could mean that you have CF. These could be lung infections that keep coming back, or problems with your digestion.

What happens before I have it?

You don't need to do anything to prepare for a sweat test.

How is it done?

The doctor will wash and dry your forearm, and will then strap two electrodes to your arm. One of the electrodes has some special medicine inside, which goes through your skin and tells your sweat glands to make more sweat, like when you're exercising!

When you've made enough sweat, the doctor will take the straps off and collect it in a special collector, which is taped to your skin so that it doesn't move. The collector has a blue dye inside it, so when your sweat goes in it turns blue! This means you can actually see your own sweat building up inside the collector!

When the amount of sweat needed for the test has been collected, the collector will be taken off your arm.

The sweat test takes an hour at most to do.

Will it hurt?

A sweat test isn't painful, but it may make your forearm red and sweaty - it will probably sweat for a few hours after you have had the test. Your arm may also feel tingly and ticklish.

What if I have any more questions?

If you have any other questions, you can ask your doctor, or chat to other people about sweat tests in the Medikidz forums and virtual world, Mediland.