Sweat test

Sweat test

The doctor wants your child to have a sweat test to find out if they have a condition called cystic fibrosis.

Key points to remember about sweat tests

  • your child is having a sweat test to find out if they have a condition called cystic fibrosis 
  • a sweat test is a safe procedure
  • it usually happens in a laboratory but it can sometimes be done in a hospital ward by the laboratory staff

Why is my child having a sweat test?

The doctor wants your child to have a sweat test to find out if they have a condition called cystic fibrosis. This is an inherited, genetic disease that causes people to have a high amount of salt in their sweat.

What's involved in a sweat test?

Laboratory staff will only need a small amount of sweat from your child's skin to measure the amount of salt. In cystic fibrosis these levels are high. In a sweat test, the skin is stimulated to produce sweat to be absorbed into a special collector and then analysed.

Will a sweat test hurt my child?

A sweat test is a safe procedure that can cause a slight tingling sensation of the skin. It sometimes causes a slight irritation. Young children with sensitive skin may have a reddened area after the test is finished which disappears quickly after a few minutes.

There are no needles used in this procedure.

Where does a sweat test happen?

A sweat test usually happens in a laboratory but sometimes laboratory staff can do the test in a hospital ward.  You can stay with your child during the sweat test.

Is there any preparation for the test?

Just make sure you don't put creams and lotions on your child's skin in the 24 hours before the test.

What do I take to the test?

Keep your child warm before and during the sweat test to encourage them to sweat. Bring a warm sweater and woollen blanket to wrap around your baby during the sweat test.  Older children will need a warm jacket or sweater to wear during the collection process. Bring something for older children to do (such as a book, colouring book etc). You will be able to feed your baby during the test.

How long will the test take?

The whole sweat test takes about an hour.

How is the sweat collected?

  • Photo of a baby having a sweat testa laboratory staff member puts a small amount of sweat stimulating liquid soaked on a gauze or gel pad
  • they put the gauze or gel pad on a small area of skin on your child's thigh or inner side of their arm
  • a mild electrical current stimulates the area that causes your child to sweat into the pad
  • this is a painless procedure that may create a tingling or warm sensation
  • after 5 minutes they switch off the current and remove the gauze or gel pad
  • for the next 30 minutes, sweat is collected on to a piece of filter paper or a small circular collector
  • the test procedure finishes when sweat collection is completed
  • the sweat collected is sent to the laboratory where they measure the salt content of the sweat
  • the laboratory sends the results of this test to your doctor within one week

This page last reviewed 18 February 2019.
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