What type of product is a common moisturizer containing ingredients to lock in hydration?

A common moisturizer designed to lock in hydration is classified as an emollient. Emollients are specialized ingredients that act as a barrier on the skin's surface, helping to seal in moisture and prevent water loss. This is essential in maintaining skin hydration, particularly in conditions where the skin may lose moisture more rapidly, such as during dry or cold weather.

Emollients typically include ingredients such as oils, butters, and fatty acids, which not only hydrate but also enhance the skin's texture, making it feel soft and smooth. They play a crucial role in a skincare routine by providing the necessary hydration that can improve skin elasticity and overall health.

In contrast, other options listed serve different functions: toners are primarily used to balance the skin's pH and remove residual impurities, serums are concentrated formulations aimed at targeting specific skin concerns such as pigmentation or aging with active ingredients, and exfoliants work to remove dead skin cells to promote cell turnover and enhance skin texture. Each of these products has its unique purpose, but when it comes to locking in hydration, emollients are the most effective choice.