It's driving me insane! He's recently started doing it and he's now got a red patch around his lips which is really sore and then he keeps licking it. If I tell him not to he immediately does it again 
. I try and smear some sudacrem on it when I get chance but he will just lick it off. I sneak in his room when he's asleep and manage to get some on at night and it does improve but not enough to withstand the constant licking during the day.
Any tips? Fairly sure loads of kids do this, just wondering if there's a more effective cream I can put on that will clear it up a bit quicker.