The first physical response to cold is an increase in heart rate and quickened breathing. The vessels in the skin pull together to prevent heat being lost through the surface of the body. Despite this, cold by itself is not necessarily a health hazard. People who are in good physical condition who eat properly and take adequate rest, can cope with cold alone. Warm clothing is obviously required. In particular, the head and the neck should be properly covered.
Hypothermia can be caused or exacerbated by insufficient clothing, going into the water and exposure to wind. Alcohol and sunburn can also aggravate the situation because they increase blood flow and that in turn causes more heat to be lost through the skin. Smoking is similarly harmful because it increases the risk of toes and fingers freezing. Where a person is at risk of drowning it is very important to get them out of the water and dry as quickly as possible. Hypothermia occurs a lot faster in water. Remove wet clothes if dry ones are available and give fluids to prevent dehydration.
When parts of the body freeze a number of physiological changes can occur:
It is important to prevent thawed body parts from refreezing during transportation of the patient to hospital, since this can cause even more damage.
If the core-body temperature falls below 35°C hypothermia can occur. Initially, a person will shiver but as their temperature decreases, this will stop. The sufferer will also be less alert and aware of what is happening. It will become difficult to find a pulse so time and care needs to be taken over any physical checks. Try to get medical help immediately. Remove all wet clothing and cover the body with coats, blankets, or even newspapers to prevent further cooling whilst waiting for help. Once in a hospital the victim will slowly be brought back up to normal temperature.