A 39-year-old reader wants to bare her feet and wear flip-flops on her holiday to Greece, but is self-conscious about her thickened and yellow big toe-nails. How can she make her feet presentable on the beach? Is this problem more common in those people with different-sized feet?

This year it will not only be holidaymakers who have to worry about fungi. The athletes who have been training in China and are now competing in the Olympics will also have to take special care of their feet. The temperature has soared during the past week, but the weather remains muggy and the smog hasn't lifted as much as had been hoped. All competitors, especially if they have fair, soft skins or sweat readily, will also have to watch for fungal growth in the groin, under the armpits and in any other clammy spot.

A single glance at the tanned faces of fellow guests at summer parties will tell who has been out in the Mediterranean sun and who has had to remain as a workhorse in Britain. A less appealing but more detailed inspection, the old-fashioned foot inspection of school days or military service, would also show that a tan isn't the only dermatological memento of a holiday in warmer climes. This is the time of the year when foot and toenail fungi run rampant. If the fungi are not controlled, they may spread to other parts of the body and become one of the infecting organisms that cause itchy, unsightly rashes in the sweaty, rather more intimate parts of the body.

Infections under the toenails are caused by dermatophytic fungi and yeasts. They are spread by running around communal swimming pools, standing on the concrete beneath the communal shower found on many continental beaches or from sharing towels and treading on well-used carpets. People who already have athlete's foot find that the condition flourishes when feet are hot and damp, as when encased in tight shoes - especially if the shoes are not allowed to dry properly at night and are not well dusted.

The effect of a nail infection is to give its tip a dirty-white or yellow hue. In time the whole nail becomes thickened as the infection spreads from the top of the toe towards its base. Later the nails of other toes become involved. As debris and fungi accumulate under the infected nails, the detritus from the infection lifts the nail off its bed and allows the fungi to spread even faster. Usually the first toes to be infected are the big toes, because they are the ones most likely to bang against the inside of the toe cap. When the whole shoe is tight, or the wearer is unusually sweaty or doesn't dry the feet thoroughly, any of the soft skin between the toes may be infected and may even split. Finding comfortable shoes is especially difficult for those people who are unfortunate enough to have one foot slightly larger than the other. It is unusual for people to be completely symmetrical.

Our correspondent, an athletic open-air woman who holidays in the Mediterranean sun, is typical of one group of people liable to suffer nail infections. Older people are also at risk, because their nails lift more readily after the repeated minor trauma as the end of the toe, which may not have such a good blood supply as it once did, strikes the inside of the shoe. This lifts the nail from the bed and allows fungi and yeasts to spread and settle. Ridding someone of fungal infections of the toes is a long job, whereas a holidaymaker who develops an itchy rash under the arms is usually readily and quickly cured by taking a fungicide by mouth or by applying an ointment or powder.

The standard good advice on how to escape foot infections is to avoid shared towels and bath mats. It is also wise to wear shoes that breathe - these are usually rather more expensive, and leather rather than plastic. It is also sensible to change socks daily. Shoes should not be too tight, as this causes pressure, but neither should they be so large that every brisk walk will batter the end of the toes. Flip-flops are ideal beachwear. Scatter fungicidal dusts in the shoes after wear and dry them carefully at night. Keep toenails short and treat any infected nail early before it has spread beneath the nail or to other toes. An easy, even if not curative, treatment is to paint an infected nail weekly with a fungicide for some months. Curanail, the trade name for amorolfine, is an excellent, easy-to-apply and relatively long-lasting fungicidal nail lacquer that is colourless.

E-mail your questions to drstuttaford@ thetimes.co.uk or write to times2, The Times, 1 Pennington Street, London E98 1TT

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