What is this? He keeps scratching

Hello - those lips look inflamed and sore and may have secondary disease eg yeast infection on top of whatever started it off.   They did ought to be checked by the vet in the context of the rest of the patient - and as lip licking, a dogs' natural response to soreness, can make things more sore very quickly, the vet may want to suggest how long it is reasonable to wait to be seen.  As to the cause there may be many possibilities, from autoimmunity to allergy to mites to systemic diseases, which is why triage - and potemtially gloves etc - are reccommended.  Please will you let us know how you get on.