Hi L.,
I agree that working with children who have developed a habit of biting when frustrated is very challenging for adults. I have some ideas, but first, I want to set the record straight: BITING A CHILD TO TEACH A LESSON IS ABUSIVE. PERIOD. There are no if's ands or buts about this. Some of us do this because that is what some of our parents did, and it made an impression. Our children trust us to find better ways to teach: we are the adults and should not sink to their level of biting, yelling or scaring them. This is going to make some people angry, but if you cannot find other ways to discipline your child, please seek some resources.
In regard to some positive actions to take to help your grandson, here are some ideas we've used at childcare centers and what I have done as a nanny.
1. Keep an eye on the child who is biting, esp. in social situations. Watch for signs of frustration, anger and move in immediately. Positioning our bodies between the children really helps, and the gentle guidance of having their need attended to before it overwhelms them is key. At childcare centers, we often had a teacher whose key focus was to shadow children who were in a habit of biting.
2. Keep teething items handy. Hard pretzels, frozen bagel slices, teethers, even a cold, wet washcloth all work better than someone else's flesh.
3. Keep redirecting. This is handy when the child bites and adult. "I don't want you to bite people. I don't like that. You may bite this instead." Hand the child something appropriate to bite and then put them down in a safe place.
4. Take extra precautions. Set up a portacrib/pack-n-play in a safe area of the house; when you must leave the children to use the bathroom, place the child who is biting in there with a pleasant activity. THIS IS NOT A PUNISHMENT, but a safety measure. If the other child would also like to enjoy the activity, let them take turns. The point is not to "favor" the biting child by taking them with us out of the room, but to be matter of fact about separating the children.
5. Keep your cool. Instead of showing our anger and outrage toward the child that has bitten, use this as an opportunity to show empathy and compassion to the child who has been hurt. "Oh, ouch. You are so sad. I see that your (hand, arm, etc.) really hurts." Our routine is to always wash off a bite gently and then apply an ice pack. If you have two adults on hand, the second one can help the child who bit get an ice pack for the first one. (Note, do not send the parent of the bit child with the biting child. Parents of children who have been bit often have very strong emotions around the incident and take this very personally. It's an affront.)
6. Give guidelines. As another mother pointed out, it wasn't the yelling or biting back that made an impact, it was the lack of contact and connectivity with the family/group. If my son and I were at a playdate and he bit someone, I would make my amends to the parent and child, apologize profusely and then leave. "Biting hurts. When you bite, we have to leave." Were he to bite at our home, he would need to go play somewhere else.
One thing to remember, and this is important: children at this age might say "sorry" with prompting, but they do not understand what sorry means. Better to model that empathy. And do not encourage the children to hug, or you might find that the biting child will seize the opportunity to bite again.
Toddlers are just learning about self-control and self-regulation. And they are still "learning the rules"...over and over and over again. It is a phenomenal achievement for a child to suppress the urge to bite, most especially when they are teething, so value the successes --no rewards, just acknowledge when they visibly stop themselves from biting. "I saw you wanted to bite Tess, and then you remembered that she is not for biting. Thank you! Here, you can bite this." Keep being clear about boundaries and be vigilant while they are going through this phase. Loving and supporting our child through the myriad challenges of toddlerhood gives them a great foundation for the preschool years, and when we guide them with love, respect, and compassion for what their abilities and personal challenges are, we give them the confidence to continue in a positive way.
My best to your family.