Milady Cosmetology Practice Exam 2025 – All-in-One Guide to Master Your Cosmetology Certification!

Glycerin is a key ingredient for hydration in skincare products due to its unique properties as a humectant. Humectants are substances that attract water from the environment and help to draw moisture into the skin. Glycerin can hold several times its weight in water, which not only helps to keep the skin hydrated but also improves its overall appearance and texture. This makes it particularly beneficial for individuals with dry or dehydrated skin, as it can support the skin's moisture barrier and prevent water loss.

In contrast, other ingredients mentioned in the options do not serve this hydrating function. Alcohol may have drying effects on the skin, as it can strip natural oils and moisture when used in high concentrations. Fragrance is typically included in products for scent, and while it may enhance the sensory experience, it doesn’t contribute to hydration. Colorants are used for aesthetic purposes to enhance the visual appeal of products but also do not provide hydrating benefits. Thus, glycerin stands out as the most effective ingredient for promoting skin hydration.