Here you can download and play with my simple skin nodes group. This nodes group is created in Blender 2.70.
Download material only (applied on suzanne):
Download Ten24 head example ( packed textures included and new peachfuzz hair ):
Scan and textures from http://www.ten24.info/?p=1164 and HDRi from http://www.hdrlabs.com/sibl/archive.html
Docs ( try to explain ):
Diffuse color: Diffuse over the skin. Simulate fine dead skin layer or any surface that not involve SSS ( like paint ).
Diffuse roughness: How rough is the diffuse , like the default diffuse node
Dermal color: Color of the skin first layers.
Dermal weight: How much the dermal take place over the diffuse
Dermal radius: How deep the light can go true this layers
Dermal textures blur: How textures (color) is blur through SSS
Subdermal color: Color of the subdermal skin layer. This layer is normally more red-orange ( muscle , blood and fat ).
Subdermal weight: How much the dermal take place over the diffuse
Subdermal radius: How deep the light can go true this layers
Subdermal textures blur: How textures (color) is blur through SSS
Specular1 color: Color of the first specular.
Specular1 intensity: Control how strenght is the first specular ( multiplied by the color ).
Specular1 roughness: How sharp or diffused is the first specular.
Specular1 IOR: Fresnel value of the first specular.
Specular2 color: Color of the second specular.
Specular2 intensity: Control how strenght is the secondspecular ( multiplied by the color ).
Specular2 roughness: How sharp or diffused is the secondspecular.
Specular2 IOR: Fresnel value of the second specular.
Normal map: Normal map can be plugged here.
Global SSS radius: Global radius ( multiplier ) of all SSS radius.
A good general document for skin and realistics human head :
The pptx is about 312mb , 308 pages with a lot of image. It’s a real bible for thoses want to achieve realistics head. I recommend it a lot.