By Melissa Jackson
BBC News Online health staff
Cast your mind back to that all-important job interview - the butterflies in your stomach, the beads of perspiration trickling down your forehead and the embarrassment of offering a sweaty palm to your prospective employer.
Sweaty palms are embarrassing
For most of us, this is an experience reserved exclusively for adrenalin-fuelled and tense episodes, but for a small minority, sweaty palms and perspiration-soaked clothes are an unwelcome daily routine.
Excessive sweating or hyperhidrosis is a condition that affects just 1% of the population.
People with hyperhidrosis produce large volumes of sweat and far more than is needed to control their body temperature.
Excessive sweat can occur on any part of the body but most often is found under the arms, on the palms of hands, soles of feet, forehead and upper lip and trunk of the body
It is not completely clear what causes hyperhidrosis and why it only affects part of a person's body.
Research does not show any changes to the structure of the sweat glands in the affected areas or how they respond.
It is thought it may be a dysfunction of the hypothalamus - the part of the brain that is responsible for controlling sweat production.
Despite its very obvious symptoms, hyperhidrosis often goes undiagnosed because sufferers do not realise that it is a recognised medical condition.
They often put up with it for years, with the resulting embarrassment it causes, which can prevent them from leading a full life because they shun normal, social activities.
Dr Mark Whiteley, a consultant vascular surgeon, who treats patients both privately and on the NHS, said: "The most socially damaging type of hyperhidrosis is the one that affects the hands.
"I've had people come to me who can't shake hands with other people and a lot of my patients have either missed out on or not gone for promotion at work because they have this embarrassing condition.
"I have seen A-level and university students who have to write with blotting paper under their hands because their perspiration smudges the ink on the paper."
Hyperhidrosis has enormous consequences which put you at a huge social disadvantage.
Dr Whiteley said: "If you are trying to court someone, one of the first things you do is hold hands and if someone then pulls their hand away and wipes their hand, it is an insult."
The good news is that it is treatable in most cases.
The type of treatment depends on where the problem lies.
Botulinum Toxin injections are useful for excessive sweating in the under-arm area.
Botulin is a poison which blocks the action of nerves that supply the eccrine (sweat) glands to stop them producing sweat.
The treatment is quick (taking about 20 minutes), reputed to be virtually painless and has no side effects.
However, it is not permanent and needs repeating, depending on dosage, on average every six to nine months.
Jane, a grandmother, who started to experience an excess of under-arm sweat when she reached the menopause, found Botulin injections helped her condition.
When she described her symptoms to the doctor she was referred to a specialist.
It was just before her 50th birthday in May 2004 and she was concerned that excessive sweating was firstly going to spoil the party outfit she was wearing and secondly cause her anxiety and ruin her enjoyment of the celebrations.
She said: "I had always sweated a lot anyway, but approaching the menopause it seemed to get worse.
"At my daughter's wedding in May 2003, the suit I wore was badly stained with sweat.
"I had my first set of injections in March this year and then went for a top-up in May, just before my birthday.
Sweaty arm pits can be treated
"The injections were quite painful, but I think they were worth it.
"Before I had the Botulinum injections, I was afraid to put my arms up because there might be sweat marks under my arms, but now I feel a lot more confident.
"On my birthday I was wearing a nice dress and no sweat marks showed through, it was lovely."
A more permanent solution to hyperhidrosis is Endoscopic Transthoracic Symathectomy or ETS - a keyhole surgery procedure, carried out under general anaesthetic - which cuts the nerves that supply the sweat glands.
Surgery side effects
ETS is 99% effective at curing palmar hyperhidrosis (sweaty hands) and, with a slight modification, can also cure axillary hyperhidrosis (sweaty armpits) in 80% of people at the same time.
The same technique, modified once again, can also be used for facial flushing, blushing or sweating - with a success rate of 70% for each side.
There is some risk of side effects, one of which is that new the sweat that should have come from these areas is re-distributed elsewhere and new areas of excessive sweating can be created, usually on the trunk and lower parts of the body.
Another, more serious but rare risk, is that the lung can get damaged during surgery, leading to a tube called a "chest drain" having to be put in place for a couple of days to make sure that the lung re-inflates.
Very rarely, the lung needs to be repaired after such an injury.
The earlier hyperhidrosis is treated, the better long-term psychological outcome for the patient, according to Dr Whiteley.
He said: "People who come in their 20s and 30s and get treated, waltz through life because they can adjust, but older patients get into ingrained habits.
"So it is better to get it done sooner, rather than later."