The dangerous period of a child’s head fall is usually around 1 to 3 days. Most children who fall on their heads will have an adverse reaction at that time, while a small number of children may have a delayed intracranial hematoma or effusion. If a child’s head fall is serious, most children will have an adverse reaction on the same day, also known as the dangerous period, often accompanied by vomiting, headache, drowsiness, loss of appetite, nausea and other phenomena, and the late untreated children’s lives may also be jeopardized. There are also a small number of children may be delayed intracranial fluid and hematoma, that is, about 3 days after the head fall before the symptoms began to appear, so parents need to observe for about 3 days, if the child has no problem, basically through the dangerous period.