Lewis sucks his thumb and has his fingers in his mouth constantly. They are looking red and sore/chapped. Is there anything i can put on?

Libby sucks her thumb and it has gotten quite bad before, red, split and weepy. We put a plaster on it but she pulled it off so we put some Savlon type stuff on it, which did help a bit. TBH though I think if it gets that sore they just won't suck them and then it gives them time to heal. xx