A condition exists which affects a persons ability to sweat normally. If the human body cannot sweat properly it is harmful because they would have difficulty cooling themselves. This condition would most directly interfere with

The body would not be able to cool itself so excess heat would remain in the body instead of being lost via evaporation of sweat. The rise in temperature would not be brought back to normal which would affect thermo-regulation in the body.
The high body temperature would most definitely affect the activity of enzymes in the body which control most metabolic reactions.