Thirst's the craving for fluids, resulting in the basic instinct of humans or animals to drink. It's an essential mechanism involved in fluid balance. It arises from a lack of fluids and/or an increase in the concentration of certain osmolites such as salt. If the water volume of the body falls below a certain threshold, or the osmolite concentration becomes too high, the brain signals thirst. Continuous dehydration can cause myriad problems, but's most often associated with neurological proble… (More on Thirst)