The most common cause of black eyes is due to low blood pressure, there is often a sudden blackness in front of the eyes when you get up after a long squat, also called postural hypotension. Because the body blood gathered in the lower body when squatting or get up instantly blood is too late to redistribute, causing the brain transient ischemia, hypoxia and lead to dizziness, black eyes symptoms, the duration will not be very long, instantly can recover on their own is a normal physiological phenomenon, do not need to be overly concerned and excessive treatment, usually pay attention to the daily life when getting up more slowly. Consider also the factor of hypoglycemia, low blood sugar when the stored energy is not enough will also cause cerebral ischemia, hypoxia, accompanied by palpitations, sweating, cold extremities and other clinical symptoms, can be effectively relieved by eating.