I am acostummed to bite the skin of my mouth and of my lip (not on shabat), is there an issue on that?
I heard that if you tear it off it’s an issur of rabanan and if you swallow it is deoraita.
It is true? What is the isur?
Is there a difference between mouth and lip?
What I do if my lip just kind of breaks?
The potential issur here is if there is a prohibition to eat human flesh. The Rambam says (Hilchos Maacholos Asuros 4-21) that it is forbidden ( M’deorayso, – an Issur Asei) to eat even the skin of a human. The Pri Migadim (Sifsei Daas Y:D 79-3) says that it could be that it is only D’rabonon ( Also see Ben Ish Chai Emor 2-5 and See Chaye Halevi 5-65(4). Others say that it is permitted (Kaf Hachayim Y:D 79-11, Maadanei Hashulchan 97-43). The Ben Ish Chai writes that one should not bite his skin because pieces might get stuck between his tech and he might end up eating them, however Kaf Hachyim ibid permits it.
There is an opinion that says (Doleh Umashke from Horav C. Kanievsky shlit”a) regarding the skin that it is preferable to be careful not to eat it, but it sounds that he holds that halachically it is permitted.