The majority of toddlers engage in some biting between their first and third birthdays. Probably the most common reason is that it is one of the few ways of communicating that's effective for them, before verbal skills are developed. However, not all children bite. Some choose other forms of communication, such as grabbing, shoving, or punching.
Another reason toddlers bite is to express frustration, a feeling which is very common with toddlers, because both their communication skills and their motor skills are so limited.
To a young toddler it can be funny to see mommy suddenly bolt upright or for a playmate to start crying. Toddlers may also bite because they're teething or because they put everything in their mouths anyway, so why not someone's arm? It could even be something as simple as hunger.
But how do you teach your child not to bite? Make it perfectly clear that the biting is hurtful and wrong and point out to your child how much pain their biting has caused. Express that biting is wrong and unacceptable and that neither mommy or daddy like it.
If you discover that your child is biting out of frustration, try giving them an alternative to express to people they are having a difficult time. Though language is a difficult task at this age, most toddlers can be taught words that are appropriate for such a situation. For instance, "You need to tell mommy or daddy that you need help and not bite us," or "Show mommy what you need, but don't bite. You'll hurt her if you bite and I know you don't want to hurt mommy, do you?"
Experts agree that parents should try not to give biting so much attention that it becomes an attention-getter. This is true of all behavior that you don't want to see repeated. Firmly tell the child again that there is no biting allowed, that it is wrong, and that it hurts people.