Primary hyperhidrosis
Most experts believe that primary hyperhidrosis is caused by problems with the sympathetic nervous system.
The sympathetic nervous system
The sympathetic nervous system controls most of your body’s functions that do not require conscious thought, such as movement of food through your body and the movement of urine out of your kidneys and into your bladder.
The sympathetic nervous system uses sweat like a thermostat. If it senses that you are getting too hot, it will send a signal from your brain to the millions of sweat glands in your body to produce sweat. The sweat cools on your skin and reduces the temperature of your body.
Sweat glands, known as the eccrine glands, appear to be involved in hyperhidrosis. Eccrine glands are present in the greatest numbers on your armpits, hands, feet and face, which may explain why these areas are often affected by hyperhidrosis.
It is thought that in cases of primary hyperhydrosis, there is a problem with the part of the brain that regulates the sweating process, that results in the brain sending signals to the eccrine glands, even though there is no need to cool the body.
Hyperhidrosis in families
Cases of primary hyperhidrosis can run in families, with 1 in 4 of all those affected having a close family relative who was (or is) affected by the condition. This would suggest that a genetic mutation is responsible.
A genetic mutation is where the instructions that are carried in all living cells become scrambled in some way, which can disrupt the normal workings of the body. Some genetic mutations can be passed down from parents to their children.
See the Health A-Z topic about Genetics for more information about mutations.
Secondary hyperhidrosis
Common causes of secondary hyperhidrosis (where there is an underlying cause) include:
- menopause – when a woman’s monthly periods stop, usually around the age of 52
- over-active thyroid gland
- being drunk on alcohol or "high" on drugs – particularly stimulants such as cocaine or ecstasy
- withdrawing from alcohol or drugs (in people who have become addicted to them)
Some types of medications can also cause excessive sweating in some people. For example:
Less common causes of secondary hyperhidrosis include:
- some types of infection, such as HIV or tuberculosis
- Parkinson’s disease – a condition that affects the way the brain co-ordinates body movements
- disorders that develop inside blood cells or bone marrow, such as leukaemia or lymphoma (both of which are cancers of the white blood cells)
