There are two main types of sweating – primary (cause unknown) and secondary.
Primary or idiopathic hyperhidrosis is when the sweat glands have bed bed in with fatty deposits that prevent the nerves from transmitting signals to them causing excessive sweating. It can be triggered by anxiety, stress, exercise, fever etc. If you have this condition it will need to be treated by a professional therapist since there are no medications available for it currently.
Secondary or psychogenic hyperhidrosis occurs when someone has an underlying psychological problem which makes them feel embarrassed about their excessive sweating so they develop strategies to cover up their problems such as wearing clothing with high necklines etc… This type of perspiration does not require treatment however one should try and avoid embarrassing triggers if possible..