This maybe a dream some one has had but it does sound very familiar to me!
This is a kids film possibly set in the desert in the future, with a boy and a dog who rescue a girl from some one who maybe her father. The father injects people in their lips with something and they have blood coming out of their lips. Sounds weird but also kind of rings a bell! Can anyone help save my girlfriends sanity?

Hmmm weird, the only thing that comes to mind is Spaceballs... but there is nothing about bleeding lips.. and I wouldn't categorize it as a kids movie...

Wish I could be of more help... Let us know if you figure it out!

Could this be it? A boy and his dog?

http://www.amazon.com/Boy-His-Dog-Hal-Baylor/dp/B0000C825J/ref=cm_sylt_fullview_prod_txt_5/002-2758340-5212865/002-2758340-5212865