Effects of exposure to heat are:

1. Heat exhaustion

2. Dehydration exhaustion

3. Heat cramps

4. Heatstroke (sunstroke).


Heat exhaustion is the body’s response to excess loss of water and salt through sweat, caused by exposure to hot environmental conditions. In fact, it is the warning that body is getting too hot. Heat exhaustion results in loss of consciousness and collapse. Before the loss of consciousness, following warning signs appear in the body:

i. Increased heart rate

ii. Increased cardiac output

iii. Dilatation of cutaneous blood vessels

iv. Increased moisture of the body

v. Fall in blood pressure

vi. Weakness and uneasiness

vii. Mild dyspnea.


Prolonged exposure to heat results in dehydration. It is due to excessive sweating. Dehydration leads to fall in cardiac output and blood pressure. Collapse occurs if treatment is not given immediately.


Severe painful cramps occur due to reduction in the quantity of salts and water as a result of increased

sweating, during continuous exposure to heat.



Heatstroke is an abnormal type of hyperthermia that occurs during exposure to extreme heat. It is

characterized by increase in body temperature above 41°C (106°F), accompanied by some physical and

neurological symptoms. Compared to other effects of exposure to heat such as heat exhaustion and heat

cramps, heatstroke is very severe and often becomes fatal if not treated immediately. Hypothalamus loses the power of regulating body temperature.


Sunstroke is the hyperthermia caused by prolonged exposure to sun during summer in desert or tropical


Persons Susceptible to Heatstroke or Sunstroke

People more susceptible to heatstroke or sunstroke are:

i. Infants

ii. Old people with renal, cardiac or pulmonary disorders

iii. People doing physical labor under sun

iv. Sportsmen involved in continuous sports activities without break.


Common features of heatstroke or sunstroke are:

i. Nausea and vomiting

ii. Dizziness

iii. Headache

iv. Abdominal pain

v. Difficulty in breathing

vi. Vertigo

vii. Confusion

viii. Muscle cramps and convulsions

ix. Paralysis

x. Unconsciousness.

If immediate and vigorous treatment is not given, damage of brain tissues occurs, resulting in coma and


Heatstroke and Humidity

Development of heatstroke depends upon humidity of the environment. If the environmental air is completely dry, exposure of body for several hours even to a temperature of 54.4°C (130°F) does not cause heatstroke. If air is 100% humid, even the temperature of 41°C (106.8°F) causes heatstroke.


Heatstroke or sunstroke can be avoided by the following measures:

i. Avoiding dehydration by taking plenty of fluids such as water or sports drinks

ii. Taking frequent breaks during work or sports activity

iii. Wearing light clothes with hat.


Person affected by heatstroke or sunstroke must be treated before the damage of organs. The subject

should be immediately moved from hot environment and hospitalized as soon as possible. Immediate cooling of the body is the usual treatment. The person must be immersed in cold water or cold water may be sprayed on the skin. If water supply is not sufficient, cooling the head and neck of the subject should be done first. Ice cubes can be rubbed on head and neck. Ice packs must be kept under armpits and groin. Cooling efforts should be continued till the body temperature falls to about 35°C


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