Not all autistic children display challenging behaviour but, children who do are more likely to hurt themselves or other children when this happens.
There are different range of challenging behaviour. It could be physical challenging behaviour like biting, hitting and spitting. Mouthing non-edible items, smearing or self injurious behaviour.
Challenging behaviour could be a way of communication for the child to let out frustration. The child may be unwell, hungry, a change in routine, transition between activities, sensory issues e.t.c. If any of these happens, it can lead to anxiety and then outburst of challenging behaviour.
KEEP A DIARY
It helps to keep a diary of what happened before, during and after the behaviour. If necessary, keep diary for a long time. That way, you can possible see a pattern.
Make sure everyone involved with the care of the child is consistent with your approach towards the behaviour.
Use short sentences. Do not overload the child with too much information. This might be hard to process. Show support towards communication to know what is getting the child upset by using visual supports.
Create a relaxed environment for the child. For example, music therapy, bubbles, warm bath with lavender. You can also provide trampoline to release energy.
Give rewards for good behaviour. That can help the child learn acceptable behaviour.
Seek professional help.
Reach out to other parents who has got kids on the spectrum.