Why would my 3 year old need to get a sweat test?

Cystic Fibrosis: Sweat tests are done to help diagnose cystic fibrosis.

Symptoms: Testing for cystic fibrosis:i would look to test a baby whose sweat tasted salty, whose stools smelled so bad they would clear a room, or who had a meconium plug at birth (failure to pass but normal rectum). Other factors like family history, a bleeding tendency, failure to grow, etc may also make this worthwhile.