Human beings are sensitive to outside temperature. To survive, the body has to maintain its internal body temperature at 98.4â—¦F. If it is cold outside, we have to insulate the body by covering ourselves. If it is hot, the temperature has to be brought down.

The skin is provided with four million sweat glands distributed all over its surface. As the temperature rises, the brain sends chemical signals to these glands and they start functioning. The body becomes drenched in a film of sweat. As this evaporates, the temperature drops. The volume of water lost in sweat daily is highly variable, ranging from 100 to 8,000 milliliters a day, depending on the outside temperature and the extent of physical activity.

Sweat if not pure water. It contains small amount (0.2 – 1 per cent) of chemicals like sodium (0.9 gram/litre), potassium (0.2 gram/litre), calcium (0.015 gram /litre), magnesium (0.0013 gram/litre) and other trace elements. When a person moves from a cold climate to a hot climate, adaptive changes, called acclimatization, occur in their sweating mechanisms, regulating not only the fluid lost but also the chemical content.

Summer months are vacation months when people travel to the hills from the plains and vice versa. If you are traveling to a warmer environment, it takes your body a couple of days to adjust to the new temperatures. The maximum rate and quantity of sweat has to increase and it has to become more dilute. This acclimatization period is the time when people are most vulnerable to the effects of heat.

The sweating mechanism is inefficient and immature in children till the age of about four. It does not function well in the elderly, the obese and those with diabetes. The system also breaks down with some of the medications taken for high blood pressure and depression.

The body’s natural cooling mechanism can fail:

• If sweat cannot evaporate because the outside environment is humid. The internal temperature continues to rise even though the body remains bathed in sweat.
• When inadequate fluid intake with dehydration prevents adequate sweating.
• Due to continuous physically taxing work or exercise in a hot environment without sufficient intake of fluids.

 To deal with summer

• Try to stay indoors as much as possible, going out only before sunrise and after sunset.
• Confine exercising outdoors to the same time. Even swimming in the hot sun can lead to heat exhaustion and stroke.
• Avoid synthetic garments. Wear clothes made of cotton, linen, jute and other natural fibres.
• Drink plenty of fluids. Do not wait to feel thirsty. The best liquids are tender coconut water or lightly salted lime juice and buttermilk.
• Avoid aerated drinks. They add unnecessary calories. Many of them are hypertonic and will not quench your thirst.
• Dehydration and the ill effects of are aggravated by caffeinated beverages, whether they are colas, tea or coffee. Alcohol has a similar effect.

 Most of live in heat radiating concrete jungles where we have to go out to work in the summer. Frequent power cuts and inadequate voltage make amenities like fans, coolers and air conditioners dysfunctional. In this scenario we have to be careful about the effects of the summer heat, particularly on the vulnerable young and old members of our families.