The barriers to absorption appear to be so perfect in certain parts of the body that we have become accustomed, either instinctively or deliberately, to discount the possibility of intoxication through them. Probably the best illustration of such disregard of potential danger applies to the every-day treatment of the skin. This surface, which, from a physiologic standpoint, is only a thick membrane, is repeatedly subjected to contact with toxic gases or poisons in solution without much fear of untoward consequences. The workman is often exposed in this way to products that would unquestionably be noxious if they were to penetrate as far as the subcutaneous tissues. With evident unconcern, the surgeon bathes his skin with poisonous antiseptics that he well knows would bring about violent reactions if they were in contact with the enteric rather than the cutaneous surfaces of his body.
In the skin and its appendages are found
THE ABSORPTION OF DRUGS THROUGH UNUSUAL CHANNELS. JAMA. 1923;81(23):1954-1955. doi:10.1001/jama.1923.02650230038015