Question:
My son bites the back of his hand when he is angry. What can I do to help him stop that?

My Opinion:
Hand biting when angry is a means of release of the anger. Some kids strike out at the source of the anger, the person who is making them angry, or perhaps another person, or the dog, etc. This is similar to mom/dad having a bad day at work and coming home and yelling at the wife/kids, kicking the dog, and putting a fist thru the door. Some kids will strike out at themselves, for several different reasons.

Does he do it because he is angry at someone or something as an external situation to himself? Or is it when he is angry at an internal situation to himself as punishment, because you, a teacher, or someone else, has punished him? Or both? That does make a difference.

I am reading your question as he is angry at an external situation, like you won't let him do something, his brother took his toy, etc. If he is biting his hand in these types of situations, it is an anger/frustration outlet. He has been taught that striking out at another person is not appropriate. But he does not know what else to do to get out his anger. I would practice other ways for him to work out his feelings. The ultimate goal for most kids, I think, is "use your words", to tell the person (or mom and dad) why you are angry and hopefully you can work out an acceptable resolution. For some kids, and even adults, physical recommendations include hitting a pillow or punching bag, throwing darts at a target (with or without a picture of the offender!!), tearing paper, hammering on rocks, etc. What you might want to do is figure out, maybe with your son's help, something else he can do to vent the anger/frustration, but it will probably at first have to include something that does have a stimulatory nature, like hitting a pillow or punching bad, which will create some sensation in his hand, rather than throwing darts, which will not do that. You can then gradually move to something you both would agree is more appropriate, and also have him use words while venting, such as yelling "at his friend" as he is hitting the pillow, etc. This can then move to just verbalizing and eventually a more calm/rational verbal response that he can actually use directly with his friend or brother or you or whoever, without the need for yelling or hitting at all. Well, such is the goal for all kids anyway.... =)

It can also be a form of attention-getting, if he is angry and he wants your attention or he is doing it "so you will see how much it upsets him so you will see things his way". You can try extinguishing by ignoring, but I think shaping a more appropriate response is better for that situation also.

If your son is biting his hand as a response to an internal situation, either as a "feel good" or as a punishment, you can let me know and I will give you my ideas on that too.