Between 0.2 and 1.0 per cent of hydrocortisone, applied to normal skin appears in the urine over a period of ten days. Stripping the skin doubles this amount and significantly alters the absorption rate curve. An occlusive dressing increases absorption ten-fold but does not basically alter the absorption rate curve. Evidence is presented suggesting that both the stratum corneum and the Malpighian/basal layers serve as skin barriers.
FELDMANN RJ, MAIBACH HI. Penetration of 14C Hydrocortisone Through Normal SkinThe Effect of Stripping and Occlusion. Arch Dermatol. 1965;91(6):661–666. doi:10.1001/archderm.1965.01600120093023