Glycerin in skin care products is known to attract water to skin and help skin feel healthier, smoother, and softer. However, recent studies have found that glycerin is far more beneficial to the skin than first believed. Here are the findings of those clinical trials.
A study conducted by Dr. Yohini Appa et al found that products containing 25% or more glycerin (aka Glycerin Cream) improve dry skin far better than lotions and creams containing little or no glycerin.
16 moisturizers (containing little or no glycerin) were tested against two high-glycerin creams over a five-year period during Winter months. The study included 394 patients with severely dry skin.
The most impressive result of this study was that the high glycerin products significantly out-performed all other products tested. The study discovered that:
Another study conducted by Dr. Donald S. Orth et al found that glycerin creams actually improve the outer layer of the skin and its moisture retaining abilities.
Different types of moisterizers were tested, along with 2 high glycerin products (25% and 40%) as well as pure glycerin for a period of 5 days. At the end of the study, the skin of patients was biopsied and examined under a microscope.
Skin treated with the non-glycerin products showed no significant improvements to the cells and structure of the statum corneum (outer layer of the skin). Likewise, skin treated with the pure glycerin showed no significant improvements either. However, skin treated with the two high-glycerin creams showed significant expansion of the cells (corneocytes) and the spaces between these cells of the stratum corneum.
These visible improvements to the skin are believed to be the basis for the superior performance of high glycerin products. Glycerin creams deliver glycerin directly into the stratum corneum. This improves the skin's moisture barrier, increasing its own ability to retain moisture, which helps the skin to naturally heal from dryness.
Orth, Donald S. and Yohini Appa. "Glycerine: A Natural Ingredient for Moisturizing Skin". Dry skin and moisturizers; Chemistry and function. 2000. Pages 213-227. CRC Press LLC.