use of Vaseline as lubrication for enema

Hi,
i have been giving my dad coffee enemas once daily. The end of the nozzle used to be lubricated wth petroleum jelly (Vaseline). Now, my dad has got some boils, cannot sit for long and gets lower back pain.
Is this anal inflammation due to use of Vaseline. I read thru the net and had mixed responses on using Vaseline as lubrication.
How can i treat this inflammation?
Alex