Unusual paleness of the mucus membranes and skin, especially noticeable in the face. Pallor can have various possible causes and is not always a symptom of disease.
Pallor can be brought on by constriction of small blood vessels in the skin, which can arise in response to shock, injury, heavy blood loss, severe pain or fainting. This restriction of blood flow to the skin ensures that the brain and other vital organs are properly supplied with blood and that body heat is conserved (at least temporarily).
Less frequently, pallor can be caused by deficiency of the skin pigment melanin that can result from spending not enough time in daylight. Unusually pale skin is also a feature of albinism.
Disorders that cause pallor include kidney failure, hypothyroidism (under activity of the thyroid gland) and anaemia. Lead poisoning is an unusual cause.