when to worry about dilated pupils, Dilated pupils, or mydriasis, can result from various factors and don't always indicate a serious issue. However, there are situations where dilated pupils could be a cause for concern If dilated pupils occur after a head injury, it could be a sign of neurological trauma and requires immediate medical attention. Certain substances like illicit drugs can cause dilated pupils. If you suspect drug use and it's accompanied by other concerning symptoms, seek help.