On skin permeability, according to Wikipedia:
"Human skin has a low permeability; that is, most foreign substances are unable to penetrate and diffuse through the skin. Skin's outermost layer, the stratum corneum, is an effective barrier to most inorganic nanosized particles."
However there is little to be found on exactly what chemicals can permeate the unbroken skin.
This paper http://oem.bmj.com/content/61/4/376.full states the following:
"Many chemicals can cross the unbroken skin."
"However, the highly lipophilic nature of most solvents can also result in dermal uptake when deposited on the skin."
Is Wikipedia's statement incorrect? What chemicals can permeate the skin, which ones cannot, and why?