Permeation of skin and eschar by antiseptics I: baseline studies with phenol

To assess how the permeability of phenol is altered by thermal injury, it was first necessary to have baselines of comparison on normal skin. Using in vitro diffusion cells and the skin of the hairless mouse, [14C]phenol was applied to skin in an aqueous medium with a reference copermeating species, [3H]methanol, and 37 degrees permeability coefficients of the pair were evaluated as functions of animal age, skin hydration, stripping of the skin, dermis isolation, and phenol concentration. Age proved to be of little consequence to permeability over a wide age range. Prolonged aqueous soaking of the skins was also without much effect. Stripping of the skin and isolating the dermis by soaking techniques allowed assessment of individual skin strata diffusion resistances. When applied to skin in trace radiochemical concentrations, phenol behaved diffusionally as an alkanol with a chain length of six. But at concentrations greater than 2% w/v, phenol facilitated the permeation rates of itself and methanol; the effect was markedly concentration sensitive and only fractionally reversible. Concentration studies using silicone rubber membranes proved that the effects on the skin were the results of destroyed barrier integrity. At 6% phenol concentration there was an essentially instantaneous, 10-fold increase in the phenol permeability coefficient, raising it to two-thirds that observed with fully stripped skin. Overall, the data suggest that the stratum corneum is proportionally impaired as the phenol concentration is increased.