Skin is precious.
As the largest organ of our bodies, its a key player in an immunological line of defense and performs an essential role in respiration in the form of perspiration. It's also extremely adept at absorbing what's applied to it - upwards of 60% that is (1, 2, 3).
Dermal absorption is one of the most efficient delivery systems to the bloodstream, so what you apply to your skin really does matter. For instance, it is believed that we absorb more chlorine by bathing or swimming in chlorinated water than by ingesting it (4).
The factors that affect skin absorption include the concentration, surface area and duration of contact, physiological condition of the skin, and what part of the body is exposed (some skin is more delicate and permeable than others)
Skin is a two-way street, expunging sweat and waste and absorbing what it comes in contact with. It needs to breathe and be nourished. Some synthetic and petrol-chemical ingredients may offer surficial moisture, but occlude the exit of sweat and waste, clogging pores and preventing skin from breathing. All the chemicals, additives, fragrances, dyes and preservatives found in conventional personal care products wouldn't be as big of an issue if our skin wasn't so darn good at absorbing stuff. But since it is, choosing clean, plant-based products is a must to maintain a healthy resilience and to keep skin functioning optimally. Opt out of PC products that contain synthetic and petro-chemical ingredients in favor of those that harness nature's healing cornucopia of nourishing plants, minerals and botanicals to keep skin young, clean, balanced and protect the plant too.
(1)Ford, R.A., Hawkins, D.R., Mayo, B.C., Api, A.M. "The in vivo dermal absorption and metabolism of [4-14C]coumarin by rats and human volunteers under simulated condition of use in fragrances." Food and Chemical Toxicology 2001;39(2):153
(2) Bronaugh, R.L., Collier, S.W., Macpherson, S.E., Kraeling, M.E.K. "Influence of Metabolism in Skin on Dosimetry after Topical Exposure." Environmental Health Perspectives 1994;102(Suppl II):71-74. www.ehponlie.org/members/1994/Suppl-II/bronaugh-full.html.
(3) Kao, J., Hall, J. "Skin absorption and cutaneous first pass metabolism of topical steroids: In vitro studies with mouse skin in organ culture." Journal of Pharmacology and Experimental Therapeutics 1987;241(2):482-487. http://jpet.aspetjournals.org/cgi/content/abstract/241/2/482.
(4) Anderson, I. New Scientist September 1996. www.triangularwave.com/f9.htm