Skin permeability, for all chemicals or just some? 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.[22][23]"

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?
"Skin's outermost layer, the stratum corneum, is an effective barrier to most inorganic nanosized particles."

But skin is quite permeable to many organic compounds. DMSO is one example, and it is warned that DMSO is a good solvent for other compounds that could be more toxic than DMSO.

Another example: we all (should) know that mercury is toxic. However, it's not going to hurt you much if you roll it around in your hand for a brief period (don't breathe in, though!). But organic mercury compounds are terribly toxic and skin permeable, including the infamous dimethyl mercury which killed a famous researcher of toxins.