Hi there ,
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Well, there are two conditions where your son could be doing such actions like sniffing , clearing throat , blinking and biting skin on his thumb , firstly this could be due to anxiety , as he is growing child and he gets anxious while discovering new things in life or on day to day basis while attending to tasks , while second reason could that he might be developing Tics , which are sudden repetitive, nonrythmic, purposeless movements or vocalization ,involving one group of muscles .
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In both cases , these actions are quite likely to become a habit/s which will be annoying to others , so you need to stop him from doing them , by telling him to stop such actions as they annoy others , plus shows others that he is not confident as a person, by making him conscious of his acts , he shall finally give up his habits , and since he is a young boy and such actions have recently started so it is the right time to stop them before they consolidate into incorrigable habits.
So, start reminding him to give up on his actions as soon as possible , give him rewards if he remains free of them for whole day , and continuously try to make him conscious of his habits and continue doing this till 1-2 months , hopefully you will see a positive outcome in this approach and his habits will start to wane , and eventually on your persistence he will grow out of these habits.
However, if no or insignificant improvement is seen in giving up of his habits , then you shall seek help of a child specialist and follow his / her advise as to how to overcome such habits.
I hope this helps..
I wish you all the best...
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