Sweat glands were small tubular structures of the skin that produced sweat.
Arkonians did not appear to have sweat glands. (ENT: "Dawn")
In 2370, when Juliana Tainer was found to be a Soong-type android, she was discovered to possess sweat glands (TNG: "Inheritance")
Mylean sweat glands produced a strong but not unbearable odor. In 2374, Neelix developed Mylean sweat glands as a result of Srivani experiments. (VOY: "Scientific Method")