Severe dark circles under the eyes of children may be caused by genetic factors, lack of sleep, heart disease and so on. 1. Genetic factors: it may be because if the child’s father or mother has dark circles under the eyes that are more obvious, he or she may inherit this condition, and it is often difficult to improve. 2. Lack of sleep: If the child sleeps late at night and does not get enough sleep, it will lead to excessive eye fatigue and slower blood circulation around the eyes, thus causing dark circles. 3. Heart disease: it may be because the child suffers from serious heart disease, most of them are congenital heart disease, which will easily lead to poor blood circulation throughout the body, and will also cause poor blood circulation around the eyes, thus forming dark circles under the eyes. Children with serious dark circles under the eyes may also be caused by other reasons, should go to the hospital in time to find out the cause.