Idaho Cosmetology Licensure Practice Exam

The correct choice is an astringent, which is specifically designed to help remove excess oil from the skin. Astringents typically contain ingredients that tighten and constrict the pores, effectively reducing oiliness and helping to prevent acne breakouts associated with excess sebum production. They often contain alcohol or other active ingredients that help control oil and refine the skin's texture.

In contrast, moisturizers are intended to hydrate the skin and prevent dryness, making them counterproductive for someone seeking to reduce oiliness. Exfoliants are used to slough off dead skin cells, which can help improve skin texture and clarity, but they do not specifically target oiliness. Serums, on the other hand, are concentrated treatments that can provide various benefits depending on their formulation, but they are not primarily used for removing oil. Thus, in this context, using an astringent is most effective for controlling and reducing excess oil on the skin.