Red blood that is capillary dilatation, the formation of the cause is not yet clear, is currently believed to be related to environmental factors, physical factors, genetic factors, drug factors and pregnancy. 1. Environmental factors: If you have been living in the plateau environment, or go out without good protective measures, long-term exposure to the wind and sun, easy to cause capillary dilatation. 2. Physical factors: prolonged exposure to cold and hot stimuli will lead to capillary tolerance exceeding the normal range, which will lead to capillary dilatation and rupture, increasing the chances of capillary dilatation. 3. Genetic factors: If the parents suffer from capillary dilatation, the next generation will have a higher chance of suffering from capillary dilatation, which has a certain relationship with heredity. 4. Drugs: Long-term use of topical glucocorticosteroids will increase the chance of having trichotillomania. 5. Pregnancy: During pregnancy, changes in hormone levels in the body can induce capillary dilatation. There are many reasons for the formation of capillary dilatation, so it is recommended to consult a doctor.