Those who plan to live or travel in the tropics must adjust to the physical stress associated with high temperatures, humidity and intense solar radiation. Usually, it takes several days, and sometimes weeks for acclimatization to occur. During this time, those planning vigorous physical activities, sports or taking arduous walks must take precautions. Those with heart or breathing disorders are at particular risk to the harmful effects of excessive heat.

What are the harmful effects of excessive heat?
Besides feeling hot, tired and irritable, there are at least five disorders resulting from excessive heat:

- The most common and least harmful development is heat cramps. This occurs during or after excise and often in active individuals in good or excellent physical condition. During exercise, the muscles generate internal heat. There is also simultaneous loss of fluids and salts. The combination of these processes results in contraction of the muscles, followed by muscle spasms and cramps. Heat cramps can occur even when outside temperatures are below body temperature. Sun exposure by itself will not cause heat cramps. Treatment consists simply of moving to a cool environment and hydration with fluids. Heat cramps can be prevented by consuming liberal amounts of fluids before exercise.

- Heat exhaustion (also called heat prostration or collapse) is a common condition related to an inappropriate cardiovascular response to high external temperatures. The onset is sudden and the period of collapse short. It occurs in both sedentary as well as physically fit individuals, but is particularly common in elderly individuals taking water pills. Symptoms preceding collapse include fatigue, anxiety, general weakness, thirst, dizziness, headache, nausea and vomiting. During the collapse, the blood pressure drops, heart rate is rapid and the skin becomes cold and clammy. Body temperature may be normal or even subnormal. Treatment consists of lying the patient down in a cool place with feet elevated and hydrating with oral fluids.

- Exertion heat injury occurs in individuals exerting themselves in conditions of high temperatures and humidity. It is more apt to happen in people who are not acclimatized, physically fit or adequately hydrated.

- In contrast to heat stroke, these individuals sweat normally. Symptoms consist of dizziness, goose flesh, headaches, delirium and sometimes loss of consciousness. Urgent medical treatment is essential and involves placing a person in a cold sheet or surrounded by ice packs to immediately lower the body temperature. Oral and often intravenous fluids are necessary, and the victim should be hospitalized for observation.

- The last heat disorder is heat stroke which occurs most commonly in the elderly who are unable to dissipate excessive heat through sweating.

- Most individuals suffering from heat stroke have chronic diseases, such as heart failure, diabetes or alcoholism, or are taking medications that impair sweating (such medicines include antidepressants, tranquilizers, beta-blockers, antihistamines, diuretics or vasodilators). Body temperatures can be very high (sometimes exceeding 41.1°C [106°F]). Symptoms may be sudden and are similar to those of exertion heat injury. Heat stroke is a medical emergency and hospital care is mandatory.

- Finally, those not acclimatized to the tropics commonly develop prickly heat rash. Essentially, the skin pores are unable to sweat sufficiently, resulting in irritation, redness and itching. Treatment consists simply of keeping cool, wearing cotton clothing and drying the body carefully after washing (especially areas under skin folds). If necessary, Calamine lotion or antihistamine creams may also be applied. Avoid powder as it may block skin pores.

Prevention of heat disorders Fortunately, there are several measures that can be taken to prevent yourself from becoming overheated, including:

- Drink extra fluids. The body adjusts to excessive heat in two ways. The first and most important way is by sweating. The body can rid itself of excessive heat by the process of evaporation. Therefore, it is important that oral fluid intake is sufficient to compensate for increased sweating in hot environments. In fact, as long as there is an adequate supply of isotonic fluids (water containing solutes such as sodium and potassium), the body can withstand very high temperatures by the process of sweating. As acclimatization occurs, the body is able to sweat more and with a lower salt content.

- The other means by which the body loses heat is by dilation of peripheral blood vessels. Sometimes this can result in swelling of the feet and ankles. The swelling is harmless and usually resolves after a couple of weeks.

- Don't overdo it. When exercising, take a break or rest if you feel hot, tired, thirsty or have muscle aches. These symptoms are often early warnings that your body may be overheating. Take heed, move to a cool place and have a refreshing drink.

- Wear comfortable clothing. Wear clothing that is loose fitting and made of porous fabrics, such as cotton. This will allow adequate ventilation, sweating and consequently loss of heat from the body. Never wear synthetic materials such as nylon or polyester. Light-colored clothing reduces heat by reflecting light. Do not wear black since this color absorbs all light. A wide-brimmed hat is recommended to reduce exposure to the sun.

- Stay in a cool place. During heat waves, get out of the sun and avoid stifling environments. Open the windows and use a fan to promote air circulation. Keep a room air-conditioned or visit an air-conditioned facility if you need to take a break from the heat.