Usually three things, a strong antiperspirant, Botox, and as of recently a select few clothing options.
One of the strongest antiperspirants out there is Mon Ray Antiperspirant. It is recommended by Dermatologist and Pharmacist to be the strongest outside of prescription.
Botox is another option but is costly. It only last four to six months and requires a physician visit. I will be the first to warn you, insurance does not cover this at all. They don't think it is a medical condition.
A great clothing option is Silverback Apparel's two lines of undershirts. They are build with a sweat proof layer to stop underarm and back sweat. They are a great complimentary solution for Botox and Antiperspirant.
Treatment is best given by a qualified medical practitioner (a doctor) - go and see one for advice.
However, Wikipedia has a good page or two on the condition (see related link below).
Generalized hyperhidrosis may affect the entire body
Dermatologists typically treat hyperhidrosis.
You can ask a thoracic surgeon. They know the causes, symptoms, and treatments for hyperhidrosis. You can learn more here: http://hyperhidrosismd.com/hyperhidrosis
The only permanent cure for hyperhidrosis of the palms is a surgical procedure known as a sympathectomy
When a person is diagnosed with facial hyperhidrosis, they tend to suffer from excessive sweating from the face, scalp or head. It is considerably more than the body requires to control its temperature. It is very common for people to be affected by hyperhidrosis, as one million people in the United Kingdom are diagnosed with hyperhidrosis.
Emotionally induced hyperhidrosis typically affects the palms of the hands, soles of the feet, and the armpits
Hyperhidrosis is not associated with increased mortality; it primarily affects the patient's quality of life rather than longevity
A group of dermatologists in Virginia reported in 2004 that 2.8% of the United States population, or about 7.8 million persons, have hyperhidrosis
Hyperhidrosis may also contribute to such skin diseases as athlete's foot (tinea pedis) and contact dermatitis
It usually begins at puberty
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This is a medical condition that is known as Hyperhidrosis. People with this disorder may even sweat in certain areas when the temperature is cool or when they are at rest. When excessive sweating is involved in hands, feet, or armpits, it is known as focal (or primary) hyperhidrosis. Primary hyperhidrosis seems to only affect 2-3% of the entire population. I suffer from hyperhidrosis myself! It isn't very fun.