Dear Readers' Clinic

I recently returned from a fortnight's cruise. Within two days of leaving Southampton, my ankles and feet swelled and it was soon difficult to wear leather shoes for the 'formal' nights. Indeed, by the final formal dinner it became impossible to wear leather shoes at all.

I have experienced this problem on all the cruises I have been on, but this recent one was the worst and, thanks to the considerable discomfort, will probably be the last.

The medical staff on the ship could not suggest a cause or treatment, and my doctor has been similarly baffled. They suggested that either the hot weather or sedentary life aboard ship had caused the problem, which was not the case; I spent more time walking from one end of the ship to the other than sitting in deckchairs! Any ideas?

M M, Glamorgan

Podiatrist, Barry Radivan, writes:

You don't tell me your age, or if you are taking any medication. But my research has potentially thrown up some information that might give you a clue to why your feet and ankles swell up when you on these cruise ships.

But, first, it is worth examining the causes of swollen feet and ankles, or oedema, as it is known in the medical profession.

There are several causes of fluid retention in the extremities. Most commonly, oedema in the feet and ankles is connected to gravity, and as we get older the veins and blood vessels that carry our blood back to up our legs towards the heart, find it harder to deliver the fluid.

The blood and body fluids become pooled and the skin starts to swell. This kind of oedema is reversible, and resting, lying down, allows the blood vessels and veins to empty and return to normal.

Some people suffer from a more serious kind of oedema, which isn't reversible, and is called pitted oedema or chronic oedema.

This kind of oedema doesn't respond much to elevating the limbs, and sufferers use water tablets and compression stocking to reduce their symptoms.

While researching the reasons why you only suffer from oedema on board cruise ships, I discovered that a number of people have experienced similar symptoms. The common denominator was that chefs on board the cruise ships were using large amounts of salt in their cooking, together with the fact that travellers tend to eat more on a cruise. Sea air contains much higher levels of salt, which adds to the problem.

Too much salt in one's diet causes fluid retention, and this could be why your feet and ankles return to normal when you return home.

Some people also have reported swollen fingers, and I myself have experienced the same, when travelling abroad, and with my index fingers becoming swollen and a bit uncomfortable.

So, if you go on another cruise, speak to a chef on board and try to arrange for him to cook up some salt-reduced foods.

Also, your GP can prescribe some water tablets to take if the fluid becomes a problem.

The only way to find out if this theory is correct is to book another cruise holiday and try to maintain a low-salt diet whilst on board. You should also drink plenty of water and get plenty of exercise.

•Barry Radivan is an HPC-registered podiatrist in a private practice in Manchester (0161 766 5564, )