I had hypnotherapy and had to try very hard not to laugh throughout it. It didn't work for me but then i'm a bit sceptical about these things so wasn't open to it - probably depends on whether you are too. I do exactly the same thing - the skin around the nails biting and it is gross. i do it to the point of bleeding and they really hurt, don't know why, according to the hypnotherapist something in my childhood made me start (yeah, uh, ok) but i don't buy that. i have now dramatically reducd my munching by getting acrylics on my nails - it's harder to get to the skin!