Which substance is an organic compound that has a super-hydrating effect on skin cells and is used in callus softeners?

• A. Glycerin
• B. Salicylic Acid
• C. Lactic Acid
• D. Urea

Answer: (D)

Urea is the substance that fits this description because it acts as a powerful humectant, drawing and holding moisture in the skin to keep cells well hydrated. It’s also used in higher concentrations in callus softeners because it has keratolytic properties, meaning it helps to soften and break down hardened keratin in thick skin. This dual action—deep hydration plus softening of the thickened outer layer—makes it particularly effective for treating calluses. By comparison, salicylic and lactic acids mainly exfoliate and break down keratin, rather than providing strong hydration. Glycerin is also a humectant, but urea’s combination of moisturizing and keratolytic effects makes it the best fit for both super-hydration and softening calluses.