Great question!
I had severe cases of eczema when I was a child, and I know how pesky and itchy it can be. I am so glad those days are over for the most part. Seldomly I will get a small rash on my arm if I let my skin go FOREVER without moisturization.
As a matter of fact, it was a hobbyist who had psoriasis that had rubbed some coconut butter on my own rash one night. He had very, extremely bad psoriasis and his whole abdomen looked very "calloused", nothing like the small quarter sized rash I had on my ankle. Needless to say, we spent a great deal of the night rubbing each other down and massaging each with coconut butter.
The second time I saw him, he had received the "shot" and his psoriasis was SO much better. The smooth parts of his skin were finally showing. I felt good for him because I knew he was always bothered by it, ecspecially BCD. But personally, after rubbing him down, I didn't feel anything "rough" on my stomache during Mish.
The best thing to do is to ask a provider if she is comfortable with your condition. There are all kinds of skin conditions out there to be concerned with (Scabies, etc.)