How do moisturizers work?

Submited by Lawrence G. Kass, M.D. on April 30, 2014

Skin moisturizer ingredients comprise three categories: humectants, emollients, and preservatives. Urea, glycerin, and alpha hydroxyl acids are humectants that help absorb moisture from the air while helping the skin retain its absorption. Emollients include lanolin, mineral oil, and petrolatum, which help fill in the spaces between the skin’s cells while lubricating and smoothing the skin. Emollients can be oil-based, which are heavier and can leave a residue on your skin and are well suited for dryer skin, or water-based emollients, which are lighter and ideal for people with normal, oily, or acne-prone skin. Preservatives, like parabens, help prevent bacteria growth in moisturizers, which may include vitamins, minerals, and plant extracts.

As skin ages, oil and dead skin clogs pores, and acne treatments dry skin, comedones, hair follicles that enlarge when they fill with dirt and oil and appear as blackheads or whiteheads, can become inflamed. Noncomedogenic moisturizers won’t clog pores, many are oil free, and are less likely to cause acne than regular moisturizers.

Protective moisturizers often contain emollients, antioxidants, and sunscreens, designed to provide a barrier that protects skin from irritants such as chemicals, free radicals, and the sun’s ultraviolet rays.

Research evaluating barrier repair emollients, such as products containing ceramides,  support repair of the stratum corneum, the outermost layer of the skin.

Serums differ from creams in what they don’t include, which are occlusive ingrediants such as petrolatum or mineral oil that keep water from evaporating. They also contain fewer lubricating agents, like nut or seed oils. Most serums are water-based, with a high concentration of active ingredients, and contain anti-aging ingredients – antioxidants, peptides, and skin brighteners. The concentration of product helps make a little go a long way, and while bottles are expensive and may be less than an ounce of product, properly used, serums can last a couple of months.

For mature skin, serums don’t offer the hydration a rich day or night cream provides, making the combination of products more effective.

References:
Bruno, K. (2014). Smoother skin in minutes a day: Protect your sexiest asset with the right creams and moisturizers. WebMD.com. Retrieved from http://www.webmd.com/beauty/advances-skin-care-9/moisturizer-toning-cream

J. N. Kraft, BSc (Hons), C. W. Lynde, MD, FRCPC.Skin Therapy Letter. 2005;10(5):1-8.

Levitt, S.  (2013). The truth about facial serums. WebMD.com. Retrieved from http://www.webmd.com/beauty/aging/beauty-smarts-serums-jan13