Car accident forehead cut a deep and large cut how long can be dangerous, according to the specific depth and the presence of large blood vessels and nerve damage and other circumstances to make a judgment, it may take a week or so. The car accident resulted in a deep and large forehead wound, if only simple relatively superficial flesh injury, in the case of clear suture timely change of medicine in about a week can grow well, without life-threatening danger. However, in more serious cases such as collision and trauma, there may be deep craniocerebral injuries or even rupture of the skull, which is not easy to judge without knowing the details. When you are admitted to the hospital, you should also improve the CT of the skull and brain and other auxiliary examinations, and you should get prompt treatment for contusions, hemorrhages, fractures, etc. It may take half a month or even longer for you to get through the danger in this case. It is recommended to consult a doctor in time when there is a car accident trauma, try to do a comprehensive cranial CT and other auxiliary examinations, to rule out intracranial injury and then take targeted treatment.