What info can an aromatherapist give?

I know an aromatherapist. I sat in on a consultation recently and the client had cellulitus. It really was very obvious that it was cellulitus. The aromatherapist said that it had been misdiagnosed and the term cellulitus was wrong. I am not a health professional, but I have seen celulitus before and the client's wife is a nurse and she agreed that that is what it is. The aromatherapist made up some oils for the client to use and he went on his way. the client has said that the oils are working well. This aromathearpist knows his stuff and is very good at what he does, but how do I tell him that I think he overstepped the mark by saying what he did. I know it will lead to an arguement and I don't really want that but he has to understand the line that can't be crossed.