I have a friend who swears by putting on lavender diffuser and some lavender oil on her 8-month olds feet to help him sleep. Is it advisable to use a lavender oil on babies so young?

I think it'll be safer to dilute the oils before application whether newborn or not. Just to make sure there's minimal reaction. I would also apply it to the pillow rather than directly on the skin. http://sg.theasianparent.com/essential-oils-for-healing-and-soothing/