self harm

my child is 21 months old boy , he is attending kindergarten for the first time three weeks back ,the problem started three days back when the school head called me and told me that my boy was bitting himself on that day and i found the bites marks on his forearm ,next day i found one bite mark on the other forearm and yesterday he came back from school with many scratch marks in his face whed i contacted the school the told me the he was scratching him self repeatedly with anger especially with changing diaper ,it is strange behaviour for me and i am a mother of 4 ,by the way 10 days back he was bitten by another child i dont know if this is relevant  
thanks

[Kevin Kennedy, Ph.D.]

Your son cannot be in kindergarten if he is only 21 months old. I assume you are referring to some for of day care program. Toddlers of this age sometimes bite themselves or scratch themselves when they are angry, and it is not necessarily a symptom of serious emotional disturbance. However, it can be a sign of Developmental Disorder/Emotional Disturbance. It is not likely that the behavior is associated with having been bitten. It is more likely a means of discharging anger and frustration. Was the behavior occurring prior to the time he was bitten?