My daughter sucks her two fingers also, not palm up. She is now 6 and the dentist said as long as she does it before she loses the two front teeth she will be fine, it won't mess her teeth up. But, her two front teeth are both very loose and she says she can't stop sucking them. The dentist showed me a metal bar they can install on her two back teeth that will make it impossible for her to suck her fingers. At 2 1/2 I would not worry too much. I will not use the liquid, or hot sauce or any of those things suggested. I think they are not safe and just plain mean.