Heres a reply from dave barker i got when i asked him about mineral oil.
"Mineral oil can make snakes shed the “stratum corneum” the outermost layer of the skin, probably because it coats the scale so completely that the underlying “stratum germinitivum” can no longer respire. It’s not good to lose too much."
Go with Nix, Provent a mite, or Soak the snakes in soapy water.
i've used mineral oil before and the outcome wasn't pretty.
Your snake will lose most of its outerlayer scales, and will look like crap.
And it takes at least 2 sheds till it looks like normal again.
if your friends have already used the mineral oil, tell them to thouroughly rinse it a few times, and get as much as it off as possible.
And if i understand correctly, they also added some in there water bowl????
if this is the case, tell them to change the water immediately.
Drinking oil wont do anything to the mites.
Grant van Gameren