This is interesting as I use le savon de Marseille for personal use and had not thought of using Savon Noir.
My Marseille is just sloshed about without a thought , but browsing through the bits of info… I note that “Savon Noir” does say to be careful to follow instructions if using on the skin…
might not be anything to worry about, but I’d have to read a bit more before using the SNoir on my beautiful visage… 
knowing me I’d get the instructions wrong so I’ll stick to Marseille