My DD is 3.5 and has sucked her thumb since pretty much day 1.. She is old enough to talk to about it and she knows we don't like it, and she asks if she can do it (only does it when tired, or upset) she also has a blankie and as soon as she sees it she goes to stick her thumb in her mouth.. It's affecting her teeth.. Her front left and the one next to it aren't straight :-( I have horrible teeth and this is a big worry of mine that my kids will have to go through what I went through as a child.. And still to this day..
She has also in the last couple of weeks started biting/chewing her nails which is absolutely disgusting so we will be trying the nail stuff for sure.now, I don't like the idea of chemicals either but hopefully she just really doesn't like the taste and hardly puts her fingers in he mouth..
Good luck ladies, we may need it lol!