Keratolytic activity of microemulsions

Area of Science:

• Dermatology
• Formulation Science
• Cosmetic Science

Background:

• Hyperkeratotic and desquamative skin conditions on the foot require effective and safe treatments.
• Microemulsions (MEs) offer potential as vehicles for topical treatments due to their unique physicochemical properties.

Purpose of the Study:

• To evaluate the keratolytic efficacy of drug-free hydrophilic and lipophilic microemulsions (MEs).
• To compare the MEs' activity against water and a 5% salicylic acid gel on the plantar foot surface.

Main Methods:

• Twenty healthy volunteers participated in the study.
• The stratum corneum of the plantar foot was dyed black and treated with hydrophilic ME, lipophilic ME, water, or 5% salicylic acid gel.
• Keratolytic activity was assessed by measuring dye removal using chromametry (a* and L values) at 24 and 48 hours.

Main Results:

• Both hydrophilic and lipophilic drug-free MEs demonstrated significantly greater dye removal compared to water.
• The hydrophilic ME showed superior efficacy to the 5% salicylic acid gel.
• MEs exhibited negligible irritation on the thick plantar stratum corneum.

Conclusions:

• Drug-free microemulsions possess significant keratolytic potential for the foot.
• The hydrophilic ME is a promising alternative to salicylic acid for managing hyperkeratotic and desquamative skin conditions on the sole.
• MEs are suitable for the elimination or prevention of plantar skin changes.