This advice comes from various parents. Attempts have been made to adequately cite references. I apologize for any mistakes or omissions.
Stephanie's Behavior Analysis of Her Son's Handbiting
Here is a great example of what a functional behavioral assessment can tell you about a problem behavior and how to change it. JB
What I have learned is to pay attention to the antecedent , the activity or moment, directly before the child bites himself. My son has three antecedents I have come to recognize as direct correlations to biting,
Frustration was the number one reason for biting with my son. If he got something wrong during his drills, he immediately bit his wrists. Therefore the suggestion for "errorless" learning was essential for us extinguishing this behavior for our son during his drills. We never have to say "No"-- you got something wrong. Instead, we prompt him through the drill and score the prompt quietly so he is not upset by getting the task wrong. Here the antecedent to my son biting himself was simply telling him "no", that's wrong.
Thirdly, my son can escalate from a calm and laughing child to where he has left himself with repeated teeth impressions on both wrists, if he is allowed to escalate from excitement. The antecedent here is usually his favorite scene in a movie that he will rewind and repeat ( a scene can be a short as three-five seconds ) over and over again. His voice will get louder, ( he says EEEEEEE a lot ), he will jump up and down and then begin biting. So by reducing his exposure or time to self-stim on the video I can effectively diminish or reduce his biting.
My child will find another SIB ( self injurious behavior ) if I do not anticipate or understand the antecedent to his behavior. Sometimes biting can occur because the self stim is the antecedent, therefore blocking ( not allowing the child to connect his mouth to his hand ) can be effective ( short term) , or gloves can diminish the effect of the bite, but this is where substitution of the SIB can also occur if the antecedent to the behavior is not discovered or dismissed.
The main thing is to understand what is happening with the child before the child bites. Try to think of the situation the child was in and say to yourself how can I create an atmosphere of understanding for the child ? Likely once this is discovered, the child's understanding will improve and you will have a win-win situation.