Not a good idea to use vaseline or other petroleum jellies on your skin or lips as there is some concern about potential carcinogenic contaminants. e.g. http://www.health-report.co.uk/petroleum_petrolatum_health_concerns.htm
Sorry the link doesn't seem to work, there's plenty of info, just google "petroleum jelly toxic".
Contaminants from petrolatum are being found in most breast cancer tissues which have been studied in recent times.
Thats a new one on me I shall have to go and look that one up....