A person with hyperhidrosis sweats excessively. Sweating is normal when the body is exposed to a warm environment, because the evaporation of sweat from the skin surface cools the body. Hyperhidrosis refers to excessive sweating that occurs when the body is not exposed to a warm environment.

In young adults, the most common cause of hyperhidrosis is emotional stress. However, hyperhidrosis may also occur with other conditions, such as heart disease, lung disease, diabetes and shock.