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Q1: I see what you say on prophylactic antibiotics (How to beat traveller's tummy, July 7), but if an attack occurs in foreign parts what do you recommend to take? Jack Barford, Guildford

A1: The size of your medical chest and its contents will of course depend on your method of travel and where you are going. If you will be in a pleasant European city with good medical facilities all that is needed are simple, immediate treatments to avoid disturbing the local doctors.

The most common problem is that of traveller's diarrhoea and therefore the smallest and simplest kit should always be prepared for this. I treat simple traveller's diarrhoea with Lomotil. The tablets are small, easy to swallow and usually without side effects apart from a dry mouth. There is a commonly held belief, one that is so frequently and firmly believed it could be referred to as a myth, that it is a mistake to take drugs to stop the diarrhoea. This myth is based on the assumption that infected faeces are, as it were, better out than in. It was believed that diarrhoea was nature's way of getting rid of the poisons. This is nonsense. Diarrhoea is nature's way of spreading the bacteria or viruses to as many other people as possible, regardless of the welfare of the sufferer. If diarrhoea is allowed to continue the inflammation of the gut and with it the diarrhoea is prolonged. This has been proved by repeated research workers having a look at the gut with a colonoscope and by careful research into the duration of symptoms in patients who have had different treatments.

Lomotil shouldn't be taken by children under nine or by patients who have any bloody diarrhoea, such as might be caused by inflammatory bowel disease or dysentry. Quietening the gut down with Lomotil is also a serious mistake if there is any question of obstruction and a distended abdomen from it. Patients should treat any dehydration before taking the Lomotil. Lomotil is a prescription drug. Immodium is not on prescription and seems almost as effective but is slightly more difficult to swallow.

When I used to go overseas with my children I always used to take oral rehydration powders such as Electrolade or Dioralyte. It is very easy to use as all that is necessary is to open a sachet and mix it with bottled sterile water, not of course tap water unless it is thoroughly boiled. If you are caught short without Dioralyte or Electrolade it is very simple to make your own mixture. Take a tumbler of boiled or sterile water and add two heaped teaspoonfuls of sugar and two or three pinches of salt, mix them thoroughly. I usually added some bottled sterile fruit juice to make it more palatable. If you are abroad and there are litre bottles about the formula is eight tablespoonfuls of sugar and one teaspoonful (level) of salt to the litre of water. If there is any question of serious dehydration in a young child, especially a baby the child should be taken as soon as possible to a doctor as in some cases a drip will be needed.

So far as antibiotics are concerned these are not indicated for treatment for diarrhoea unless it is bloody diarrhoea and the patient has an appreciable fever. I then, in the absence of laboratory facilities, tend to use Ciproxin ciprofloxacin. This is also used in smaller quantities for prophlyactic treatment where it relies on keeping a disease at bay. It is only indicated in special circumstances as it increases the risk of resistance to the antibiotic.

Q2: Medicated soap gives a false sense of security and has been found not useful in reducing antibiotic resistant bacterial infection. So please don't waste your money buying medicated soap. Dr Kadiyali M Srivatsa, Guildford

A2: Medicated soap shouldn't give a false sense of security as everyone should know that the most important aspect of washing the hands, whether medicated or otherwise, is the washing technique. The golden rule is to continue to wash the hands until the hand washer has completed singing (under their breath) the opening bars of Happy Birthday to You twice over. Neither medicated soap nor gels that can be squeezed out onto dry hands replace the need for thorough washing. Even so a medicated gel, or solution can be useful as a second best measure if no water is available. The evidence is that medicated soap is rather better than ordinary soap but the crucial factor in hand washing is the water and the length of time that is taken to carry out the procedure. Fingernails should also be kept short and nail brushes used to scrub them each time the hands are washed.

Q3: I am very fair-skinned and I seem to have developed an allergy to the sun which shows itself in prickly heat only in areas exposed to the sun. I cover up, use factor 30 suncream and stay in the shade during the hottest part of the day. I'm going on a charity trek in South Africa at the beginning of November, their spring, and I'm wondering whether I should take an antihistamine as well as my usual precautions, to ward off the dreaded prickly heat? If so, should I ask my doctor to prescribe or would an over-the-counter one be ok? Hazel Walker, Leigh on Sea, Essex

A3: Prickly heat can be a very tiresome condition and is liable to be recurrent. Some of the antihistamines are better than others at ameliorating the itch but the essential aspect of the treatment is to avoid when possible the conditions that favour it. Its cause is unknown but it seems likely that it is related to sweat drying or remaining longer than usual on the skin because the humidity is such that it doesn't evaporate properly or quickly. As with many skin irritations some relief is achieved by a cold shower, or if the trouble is limited to the arms, the immersion of these under a cold tap. The skin should be carefully dried by dabbing and calamine lotion then applied, also with a dabbing motion.