My seven-month-old son has started to bite his mother's breast nipple when she's breastfeeding him. Any ideas on how to make it stop?
The main way that worked for us was any time he bites, take him away and don't let him feed for a few minutes. If he continues, actually put him down on the floor for a few minutes. Say something while you're doing it so he knows what's going on - don't get mad or yell, just tell him "No thank you, biting hurts. Mommy doesn't like that." They usually catch on after a while.
You also might consider keeping a teether nearby and inserting that whenever he bites; odds are he's teething and will appreciate the teether.
At 7 months, the various responses are unlikely to have that much affect, so while your wife could try removal from the breast / firm no / etc the problem will have probably fixed itself before they work.
The key is to pay attention to the change in latch which usually signifies baby is going to bite (babies can't bite while latched properly - the tongue covers the lower teeth) and then swiftly remove the baby from the breast, and either re-attach baby or offer a distraction.
I would recommend against shouting at or deliberately startling baby, because this can cause a nursing strike.