Parents have been given tips on how to help their child cope with a traumatic event.
More than two thirds of children will experience at least one traumatic event by the age of 16, according to new guidance from the Institute of Health Visiting.
This can range from large scale incidents such as the Grenfell Tower tragedy and recent terror attacks to more common events such as car accidents and operations.
Other examples include experiencing or witnessing violence, abuse, serious illnesses or dog bites.
The IHV has worked with the Mental Health Foundation to develop new guidance for both health visitors and parents to help them support children after trauma.
The organisation said children are likely to experience a range of changes in their thinking, emotions, behaviour and physical responses.
For most youngsters, these symptoms will go away on their own in a few weeks but 10-30% of children go on to develop post-traumatic stress disorder.
The new guidance for parents suggests that they should seek help from their GP if there is no improvement in their child's reactions after a month.
Family doctors can refer children to more specialist psychological help.
"We very much hope that this new guidance will help both families and health visitors manage these enormously challenging circumstances with more knowledge of what will help," said Dr Cheryll Adams, executive director of the Institute of Health Visiting.
Dr Camilla Rosan, clinical psychologist at the Mental Health Foundation, added: "Experiencing a frightening event can understandably really shake up a family and it can be hard to know what to do for the best.
"Many families find it particularly challenging to know how to support younger children and infants who might not be able to clearly let you know, or even be aware, how the traumatic event might have affected them.
"We hope that these materials will help reassure professionals and families that changes are completely normal and, for most children, will not continue beyond a few weeks.
"However, for those that do not get better on their own, it reaffirms the importance of seeking professional mental health support and accessing evidence-based treatments."
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