Which type of emulsion contains water and permits incorporation of additional water, and is not removed from the skin after washing?

• A. W/O emulsions
• B. O/W emulsions
• C. Hydrophobic ointments
• D. Gels

Answer: (A)

Water-in-oil emulsions have water droplets dispersed in an oil continuous phase. Because the outer phase is oil, the surface on the skin remains oily and isn’t easily washed away by water, so the emulsion tends to stay on the skin after washing. These systems also can take up more water by forming additional water droplets within the oil phase, increasing the internal water content without breaking the emulsion. In contrast, oil-in-water emulsions have water as the continuous phase and are more readily removed by washing, and hydrophobic ointments or gels are not emulsions of this type.