You can start by avoiding the following things: hot spotlights, the stress of public speaking, being overweight and drinking alcohol. All of which may or may not mean that Charles Kennedy, the leader of the Liberal Democrats, was more likely than most to perspire when he delivered his party conference's climactic speech at the weekend.

"Charles Kennedy has always looked to me like he's slightly florid anyway so he may have a temperature control problem and therefore he will sweat," says Michael Rennie, a clinical physiologist at the University of Nottingham. "As well as temperature, if you have a substantial number of things that will activate the nervous system, like stress, then you'll sweat more," Rennie says. Any extra subcutaneous fat Kennedy may be carrying would also make the situation worse.

If horses sweat, men perspire and ladies glow, then all three have their autonomous nervous system to thank. That means that sweating (or perspiring or glowing) is a reflex action and independent of direct messages from the brain. Some people have a more responsive nervous system than others, so while one is cool under pressure, another finds unflattering pictures printed in newspapers. Kennedy has this week denied suggestions he has a drinking problem, which is just as well given that alcohol can effectively reset the nervous system to produce yet more sweat.

But short of crash diets, lowering the lights and asking the audience to leave, is there anything politicians can do to reduce the visible proof that politics is 1% inspiration and 99% perspiration?

"There are a couple of medications that might work," says Antranik Benohanian, a dermatologist at Montreal University Hospital, who has treated more than 5,000 patients with hyperhydrosis, the clinical term for excessive sweating. Some of these can be used on specific areas of the body, mainly by targeting a neurotransmitter called acetylcholine, which is produced by nerve endings under the skin and turns on the taps when it reaches the sweat glands. Applying it to the hairline the night before a big speech could prevent a sweaty forehead the next day. "But there is no solution without side effects," warns Benohanian. Some treatments merely shift the damp patches to other areas, and some induce blurred vision and a dry mouth - hardly inspiring stuff for a would be prime minister.

Another possibility is the botox injections favoured by the wrinkle-free rich. The toxin knocks out acetylcholine transmission in the target area, offering up to a year of reduced sweating. Liposuction can also destroy nerve endings beneath the skin, stopping the sweat message from being sent.