A cosmeceutical is best defined as?

A cosmeceutical is defined as a cosmetic product that also has therapeutic properties, offering benefits beyond mere aesthetics. This definition encompasses products formulated to not only enhance beauty but also to improve skin health, addressing specific skin concerns through active ingredients. For example, a moisturizer that contains antioxidants or peptides serves a dual purpose: it hydrates the skin while also contributing to rejuvenation and protection from environmental stressors.

The other options do not capture the essence of what a cosmeceutical is. A spa treatment that includes cosmetics may utilize products with beauty benefits, but it does not inherently imply therapeutic qualities. An ancient Greek process of creating pigments refers to historical practices without relevance to modern definitions of cosmetics or their therapeutic uses. Lastly, the definition of a type of manicure does not relate to the concept of cosmeceuticals, which are specifically associated with skincare treatments rather than nail care. Thus, C is the accurate definition, as it uniquely combines cosmetic and therapeutic aspects.