Q. I had red wet cracks at the corners of my mouth. I began using Mentholatum on my lips every night. That cleared it right up with no recurrence!
A. Laboratory research has shown that camphor and menthol, the active ingredients in Mentholatum, have anti-fungal activity (Phytotherapy Research, April 2003). That may explain why Mentholatum worked against angular cheilitis (cracks at the corners of the mouth). This can be caused by a fungal infection.
Vicks VapoRub has similar ingredients and might work in a similar manner. With either product, take care not to ingest the ointment. They are intended for external use.
You can read more about angular cheilitis here.