Originally Posted by
4eyedbuzzard
While the warnings regarding inhalation, ingestion, and mucus membrane absorption are valid, I believe dogwood is overstating the potential dangers of transdermal absorption of permethrin by lumping the potential transdermal route with the other ways permethrin can get into the body. Transdermal absorption of permethrin, even when applied directly to human skin is very low, around 1 to 2% at most even when applied "wet" to skin. If if wasn't, scabies creams, which are typically a 5% concentration (10 x higher than clothing spray), applied all over the infested person's body and left on for for 8 to 16 hours wouldn't be the most widely used treatment for such conditions. Additionally, permethrin is not soluble in water. And sweat is basically water. This explains why permethrin holds up to multiple launderings in water and detergent, and why it shouldn't be dry cleaned as the non-water solvents used in dry cleaning DO remove it. It does wash out eventually, and spray on types don't bind as well to fabrics as the factory applied treatments, but both are due to the permethrin molecules mechanically getting knocked off of the fabric by agitation - not dissolving in the water. Once it dries on clothing, the chances of transdermal absorption to any degree are exceedingly low. Note that even outerwear comes in contact with skin at some point - shirt sleeves, collars, cuffs, hats, socks, etc., and that factory treated clothing carries no cautions about wearing tee shirts, socks, hats, etc., next to skin.