Which function of the skin allows topical medications to be applied?

• A. Absorption
• B. Protection
• C. Sensation
• D. Excretion

Answer: (A)

Absorption. The skin’s ability to take in substances from the surface is what makes topical medications workable. Although the skin acts as a protective barrier, drugs formulated for topical use must cross the outer layer, the stratum corneum, and then move through the epidermis and into the dermis where they can act locally or enter the bloodstream for systemic effect. The speed and extent of absorption depend on the drug’s properties (like lipophilicity and molecular size), the formulation (cream, ointment, gel), hydration, and how the skin is treated (occlusion, area of application). Other roles of the skin, such as protection, sensation, or excretion, are important for its overall function but do not describe the process that enables applying topical medications; absorption is the mechanism that explains how those medications enter the skin.