Dehydration

Dehydration is the removal of water (Greek hydor) from an object. Commercially, dehydration is used to preserve food, especially fruits that normally have a high water content and are prone to spoilage. Examples are prunes, raisins, figs, and dates.

There are many methods of dehydration, with the most common being the application of dry heated air. This causes evaporation of the surface water, which is replaced by water internally.

In humans dehydration can be caused by a wide range of diseases and states that impair water homeostasis in the body.

Examples are :

infectious diseases
- yellow fever
- cholera
- Shigellosis
- common gastrointestinal viral, bacterial infections resulting in vomiting and diarrhea

external or stress related causes
- Hyperthermia
- shock
- blood loss or hypotension due to trauma
- prolonged physical activity without consuming adequate water, especially in a hot environment

dietary imbalances due to
- nausea
- restricted salt diets
- excessive consumption of alcohol

other causes of obligate water loss or electrolyte abnormalities
- severe hyperglycemia

Symptoms may include headaches similar to what is experienced as a hangover, and lower blood pressure and a dizzy feeling when standing up which is called orthostatic hypotension. Extreme cases of dehydration can result in unconsciousness and death.

Correction of a dehydrated state is performed by rehydration, and the addition of necessary electrolytes.