You are right in saying that excessive licking leads to lip-lick dermatitis
Ask your son to stop licking the lips immediately.
Frequent application of vaseline will work.
Its better to avoid otocomb ointment because it contains aminoglycosides along with steroid
. Aminoglycosides themselves have sensitizing potential.
If he does not improve with vaseline, then you must take a dermatology opinion.
Dr. Ajit Singh
MD - Skin & VD