9.7.1.2　Manners to promote the penetration of OCAs

The barrier function in the stratum corneum prevents the penetration of OCAs，which requires a longer time for skin OC.However，the long-term application of hyperosmolar OCAs may cause skin damage.Some methods to accelerate the penetration of OCAs are as follows：（ⅰ）Chemical enhancers：azone，oleic acid，dimethyl sulfoxide（DMSO），propylene glycol and thiazone can enhance the permeability of OCAs.At present，these chemical enhancers are seldom used in vivo，and their safety and penetration effect need to be further studied.（ⅱ）Physical methods to remove the stratum corneum surface layers：e.g.，adhesive tape，and microdermabrasion.（ⅲ）Other factors：e.g.，photothermal，laser，electrophoresis，and ultrasound.Although these methods can improve the effect of OCAs and reduce the action time of OCAs，they may have other side effects.For example，some chemical enhancers can be toxic to the human body，and physical methods can also cause skin damage.(https://www.daowen.com)