Extreme thirst is always present in the early stages, and young children may show marked irritability. With severe dehydration there is increasing weakness and lethargy and the urge to drink may be lost.
In children, dehydration can set in alarmingly quickly. Signs of dehydration can be dry or chapped lips, oral dryness, restlessness and dry eyes. Alarming signs of advanced dehydration in infants include a weak pulse, shallow breathing and a blue tinge to the skin, which also feels cold to the touch.
A valuable method of assessing dehydration in children is by gently pinching up the skin on the side of the abdomen. On releasing, it should immediately return to normal. When dehydration is present the skin fold takes much longer to return.
Adults could feel dizzy, be extremely thirsty and have a heightened body temperature, although their skins may also feel cold to the touch. As a result of the loss of sodium and potassium, nausea and muscle cramps can also be present. If the body continues to dehydrate, blood pressure will drop even further, resulting in shock and damage to internal organs such as the liver, the kidneys and the brain.