Hi. DD 2.5 had a red pimply rash round her mouth which we identifid from the net - and the Dr confirmed, was peri oral dermatitis.
We tried various different creams from the gp for months - none of which worked.
In the end I found a US website where people raved about the effect of apple cider vinegar on treating this condition.
We ordered some organic apple cider vinegar from a UK website and applied it twice a day for a couple of weeks using cotton wool.
She smelled a bit like a chip shop and resisted having it applied (but we bribed her) - but it worked.
I'm not a health professional but I would definitely recommmend trying this