Here is a subsurface scattering skin shader for the latest release (4.4.40), that should work on every real world scaled head.
There are two image map shaders included: one for the skin texture (if you want to use your own texture, set the density colour of the glass shader to white and connect the image map shader to the volume colour function). If not, you can delete the image map shader.
The other one is for a displacement (or bump-) map. It should go into the surface layer's displacement slot, since the glass shader has no displacement function. The surface layer has "Apply colour" unchecked and is only the carrier for the displacement. I think it's more versatile than just adding a displacement shader after the glass shader.
Of course you need to use the path tracer!!