Hyperhidrosis (excessive sweating) can be divided into 2 types, depending on whether an obvious cause can be identified. These are known as primary and secondary hyperhidrosis. Primary hyperhidrosis – Hyperhidrosis that has no obvious cause is known as primary hyperhidrosis. Although it’s not clear why it develops, it’s thought to be the result of a problem with part of the nervous system called the sympathetic nervous system, and it’s possible your genes may also play a role. Secondary hyperhidrosis: Hyperhidrosis that can be identified, it’s known as secondary hyperhidrosis.