My parents put the bandaids on my thumbs for me! Took a couple of weeks, but i stopped. My partners parents went to the extreme, and promised his sister(when she was 6) that if she stopped sucking her thumb constantly (she had her thumb in her mouth if she wasn't eating or drinking, no matter what the time of day) and promised her a kitten! It worked-it took 2 months and everytime she put her thumb back in, she lost a day off her chart.

The cat only died in the last few years at 24 though.........

I've had a bit of success with fabric bandaids (really thick sticky ones). You can also get this yucky tasting nail polish for nail biters, that seems to help too. We also tell my daughter to sit on her hands if shes being forgetful. It is a constant battle & she will grow out of it. Good Luck.