chapter  15
Effects of Occlusion: Percutaneous Absorption
ByHongbo Zhai, Howard I. Maibach
Pages 12

Occlusion means the skin covered by tape, gloves, impermeable dressings, or transdermal devices. Certain topical vehicles may also act as ‘‘occlusive dressings’’ if they contain fats or some polymer oils, reducing water loss to atmosphere. In healthy skin, the stratum corneum typically has water content of 10% to 20% and provides a relatively efficient barrier against percutaneous absorption of exogenous substances (1). Skin occlusion can increase stratum corneum hydration, and hence influence percutaneous absorption by altering partitioning between the surface chemical and the skin due to the increasing presence of water, swelling corneocytes and possibly altering the intercellular lipid phase organization, also by increasing the skin surface temperature, and increasing blood flow (2-4). Occlusion may enhance drug efficacy (5-10). Actually, skin occlusion is a complex event producing profound changes and influencing skin biology as well as wound healing processing (11-27). In general occlusion can, with exceptions (2,4,28,29), increase percutaneous absorption of topically applied compounds (30-42); even a short time (30min) occlusion can result in significantly increased on penetration and horny layer water content (43). However, effects of occlusion on absorption may also depend on the anatomic site as well as vehicle and penetrant (32,37,44).