If there is blackness in front of the eyes, general sweating, dizziness or lightheadedness, the following two conditions should be taken into account. 1. For young people, there is no hypertension or arteriosclerosis as such diseases. The first thing to consider is the possibility of insufficient blood supply to the brain, such as if often stay up late or excessive fatigue, may reflexively cause a drop in blood pressure caused by these symptoms. You can go to the neurology department of a regular hospital for a checkup, do transcranial Doppler and let the doctor measure the blood pressure to see if there is a significant drop in blood pressure. For the elderly, if there is atherosclerosis, the first thing to consider is whether there is a brain lesion, such as cerebral blood supply deficiency and cerebral infarction.