My son has started smearing; this is especially a problem at night.
There can be a sensory motivation to smearing. It may be that the texture is something that your son enjoys. Could your son have something such as play dough in his room that he could be redirected to instead?
It may be that your son is bored and does not know what else to do in this time, especially if it when everyone else is in bed. If it is safe to leave your son in his room alone, could there be activities left in his room that he could be directed to at night? A particular box of activities could be left as activities to do at night.
It is also possible that the reaction your son gets from people when he smears is reinforcing the behaviour? If he gets a lot of attention and fuss made of him he may find this exciting. It would be worth using a behaviour diary to see how people react to him when he does this. If he gets a lot of attention, try and react to the behaviour as neutrally as possible, with no eye contact and very little conversation. This can also be coupled with a lot of attention being given when he does something positive.
It may be easier to try and make it harder for your son to be able to smear. There are all-in-one pyjamas and vests that are designed for children of a wide range of ages (for details please see 'useful contacts').
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