We have been experiencing some really hot days in Jamaica, and the cry on many lips is that it is not yet summer!

The healthy human body maintains its internal temperature at around 37°C. Variations, usually of less than 1°C, occur with the time of the day, level of physical activity or emotional state. A change of body temperature of more than 1°C occurs only during illness or when environmental conditions are more than the body’s ability to cope with extreme heat.

As the environment “warms-up”, the body tends to do the same. The body’s internal “thermostat” maintains a constant inner body temperature by pumping more blood to the skin and by increasing sweat production. By doing so, the body increases the rate of heat loss to balance the heat burden. In a very hot environment, the rate of “heat gain” is more than the rate of “heat loss” and the body temperature begins to rise. A rise in the body temperature results in heat illnesses, which can have serious effects on the body.

Evaporation of sweat from the skin cools the body.

What are the effects of heat on the body?

When the air temperature or humidity rises above the range for comfort, problems can occur.

As the temperature increases, persons may experience:

• Increased irritability

• Loss of concentration and ability to do mental tasks

• Loss of ability to do skilled tasks or heavy work

In moderately hot environments, the body “goes to work” to get rid of excess heat so it can maintain its normal body temperature. The heart rate increases to pump more blood through outer body parts and skin so that excess heat is lost to the environment, and sweating occurs. These changes place additional demands on the body. Changes in blood flow and excessive sweating reduce a person’s ability to do physical and mental work. Manual work creates additional metabolic heat and adds to the body heat burden.

The risk of heat-related illness varies from person to person. A person’s general health influences how well he/she adapts to heat (and cold).

Persons who are overweight or obese often have trouble in hot environments as the body has difficulty maintaining good heat balance. Age, poor general health, and a low level of physical fitness can also make people more susceptible to feeling the extremes of heat.

Medical conditions such as heart disease, high blood pressure, respiratory disease and uncontrolled diabetes may contribute to challenges of increased heat and individuals affected with these conditions need to take special precautions. Additionally, those individuals with skin diseases and rashes may be more susceptible to heat. Substances — prescription or otherwise — can also have an impact on how people react to heat.

What are the illnesses caused by heat exposure?

1. Heat oedema is swelling which generally occurs among people who are not acclimatised to working in hot conditions. Swelling is often most noticeable in the ankles.

2. A heat rash is a cluster of small itchy, pimple-looking red blisters that appear on the skin – usually on the neck, groin, chest or in the elbow creases. In most cases heat rash will disappear when the affected person returns to a cooler environment.

WHAT TO DO

• Stay in a cool, dry place.

• Keep the rash dry.

• Use powder to soothe the rash.

3. Sunburns are caused by damage to the skin by ultraviolet rays. The skin appears red, warm, and tender and occasionally itchy. The skin will begin to flake and peel after a few days.

WHAT TO DO

• Stay out of the sun until the sunburn heals.

• Put cool cloths on sunburned areas or take a cool bath to help relieve the pain.

• Put moisturising lotion on sunburned areas.

• Do not break blisters.

• Drink extra water.

4. Heat cramps are sharp pains in the muscles that may occur alone or combined with one of the other illnesses caused by heat. These cramps occur during or after intense exercise and sweating in high heat. Sweating depletes the levels of salt and water in the body. The low salt levels in the muscles cause painful cramps. Inadequate fluid intake often contributes to this problem.

WHAT TO DO

• Stop physical activity and move to a cool place.

• Drink water or a sports drink.

• Wait for cramps to go away before engaging in any more physical activity.

Urgent medical attention is needed if:

• Cramps last longer than one hour

• Affected person is on low-sodium diet or has a heart condition

5. Heat exhaustion is caused by loss of body water and salt through excessive sweating. It is most likely to affect the elderly, people with high blood pressure and those who work in hot environments.

Symptoms of heat exhaustion may start suddenly, and include: nausea , irritability, headache, dizziness, fatigue, thirst, heavy sweating, decreased urine output, and elevated body temperature

WHAT TO DO

• Get medical aid.

• Move to a cooler, shaded location.

• Remove as many clothes as possible (including socks and shoes).

• Apply cool, wet cloths or ice to head, face, or neck. Spray the body with cool water.

• Drink water, clear juice, or a sports drink.

Heat exhaustion can lead to heat stroke if left untreated.

6. Heat syncope is heat-induced dizziness and fainting that usually occurs when someone stands for too long or gets up suddenly after sitting or lying down. This is caused by temporarily insufficient flow of blood to the brain. It can also be caused by vigorous physical activity for two or more hours before fainting happens. It is caused by the loss of body fluids through sweating, and by lowered blood pressure due to pooling of blood in the legs. Heat syncope occurs mostly among unacclimatised people. Recovery is rapid after resting in a cool area.

7. Heat stroke is the most serious type of heat illness and is a medical emergency.

• Symptoms of heat stroke include hot, dry skin or profuse sweating, very high body temperature, confusion, loss of consciousness and seizures.

First aid for heat stroke includes:

• Get the person to hospital immediately.

• Stay with the person until help arrives.

• Move him/her to a cooler, shaded location.

• Remove as many items of clothes as possible (including socks and shoes).

• Wet the person’s skin and clothing with cool water.

• Apply cold, wet cloths or ice to head, face, neck, armpits, and groin.

• Do not try to force the person to drink liquids.

Delayed treatment may result in death.

Dr Jacqueline E Campbell is a family physician and radio show host. She is the author of the book A patient’s guide to the treatment of diabetes mellitus. Email: drjcampbell14@yahoo.com IG: dr.jcampbell