By Dr Fiona de Ferrars and co-author James de Ferrars

The country was basking in a heat wave as I wrote this article and I am hoping that all the holiday makers are going to be as lucky when this article is published in August.

In England, an average temperature of 30c by day and 15c by night for two consecutive days triggers an official health alert. In 2003, the heat wave resulted in 2,000 to 3,000 more deaths than usual.

Heat exhaustion and heat stroke are two serious conditions which can result from excess heat caused either by the weather or strenuous exercise. You are at increased risk if you visit a hot country, as it takes a week to become adjusted to a high temperature and to increase sweat production from the English norm of about 1 litre an hour to a maximum of three litres an hour!

Most of us have experienced mild problems with being too hot. I can remember having a headache and feeling sick on holiday in the South of France when I was in the sun for too long without a hat. I needed shade and a drink to cool down. If this is not done, then symptoms worsen and heat exhaustion may develop. This is characterised by muscle cramps, feeling weak, heavy sweating and a rapid pulse. The heavy sweating causes dehydration and so urine becomes dark and smelly; the patient becomes dizzy as the dehydration causes a low blood pressure. If this heat exhaustion is not treated, the patient will eventually have sweated so much trying to keep his/her body cool that s/he becomes dehydrated, and heat stroke develops. Heat stroke is much rarer and more serious, and occurs when the body is no longer able to cool itself by sweating, and so the body temperature becomes dangerously high, and may exceed 41c. The symptoms are easy to spot as they include confusion, seizures, becoming unconscious and then death. Sun stroke is when these symptoms are caused by prolonged exposure to sunshine.

Infants, toddlers, those with breathing problems and the elderly are particularly at risk of heat stroke during hot weather, as their bodies are unable to get rid of heat by sweating. Young children are unable to remove their own clothes, and trust an adult to notice their hot, red faces and remove their clothing. Dogs also overheat easily as they do not sweat through their hair, and rely on panting and sweating through their feet pads to get rid of heat. Never leave a child or dog in a car when it is hot as they may die. In a heat wave of 33c a car becomes a solar oven and can rapidly reach 65c or higher, even when the windows are slightly open.

Heat exhaustion can usually be treated at home by giving fluids and resting in a cool dark room. The fluids can be given by small sips if the patient is nauseous. If the vomiting prevents adequate rehydration then admission to hospital will be needed for intravenous fluids.

Muscle cramps can be very painful and if these do not respond to electrolyte replacement drinks, ibuprofen and stretches, then admission to hospital may be necessary.

It is important to recognise the more severe symptoms of heat stroke as this is life threatening and the emergency services should be called.

The patient should have their clothes removed and be sprayed in cool water. Rehydration should continue until the patient begins to urinate.

Anyone who has suffered from heat exhaustion needs to be more careful as they will be prone to experience it again.

It is better to avoid getting heat related illnesses, than to have to treat them.

Think about and understand your environment. Anyone can become ill if they are not careful. Wear a wide brimmed hat, sunglasses and loose, lightly coloured cotton clothes which cover the skin. Keep out of the mid-day sun and avoid strenuous exercise when it is hot.

Always drink plenty of fluids, and do not go for a long walk without a good water supply, even if this means carrying a heavy rucksack.

Keep your urine clear. Incidentally, concentrated urine is more likely to cause kidney stones too!