Cosmetic creams: Classification of products by function can clear consumer confusion

October 1, 2008

The abundant array of cosmetic creams on the market can be a source of confusion for consumers. Categorizing products by function provides a method for understanding their ingredients and benefits.

Key Points

Chicago - Categorizing moisturizers based on product function resolves confusing cosmetic cream conundrums, according to Zoe D. Draelos, M.D.

"Classification in a functional hierarchy offers a rational method for understanding the actions and benefits of these products and their ingredients," says Dr. Draelos, a private practitioner and clinical researcher in High Point, N.C.

Categorizing products

At the most basic level are products that make the skin feel smooth and soft. The second step includes products that increase skin hydration. The third level refers to products with ingredients that improve the optical appearance of the skin. At the highest level, products provide all three of the foregoing functions and incorporate technology for delivering cosmeceutical ingredients to the skin.

"Ascending up this ladder, the products go from the oldest to newest, the least costly to the most expensive, and the simplest to the most technically complex," Dr. Draelos tells Dermatology Times.

Emollients

Products that make the skin feel smooth and soft are emollients, which have only a physical effect on the skin surface. They do not change the structure and function of the skin, and they do not provide moisturization.

"Emolliency is the ability of a cream to deposit between desquamating corneocytes and smooth down the corneocyte layer.

"This activity is important, because it results in reduced surface friction and a tactile sense of smoothness that is immediately appreciated by the user. However, there is no effect on skin barrier function, and emolliency is a temporary effect," Dr. Draelos says.

Products in this category commonly contain silicone derivatives, vegetable oils, cetyl or stearyl alcohol, and/or petrolatum derivatives.

Hydrating the skin

Products that increase skin hydration have a medically relevant benefit for decreasing fine lines. In fact, most clinical studies of moisturizers examine this attribute as the endpoint of product performance, Dr. Draelos says.

However, "moisturizer" is a misnomer for these products, because they do not add moisture into the skin. Instead, they create an artificial barrier, working their way into the widened intercellular spaces between corneocytes where lipids have been removed by overwashing.

This barrier prevents water in the skin from evaporating into the environment. Since it also protects the skin from irritants, these products can alleviate the stinging, burning and itching that accompany barrier destruction.

However, Dr. Draelos says, "It is difficult to maintain water in the skin without repeated application."

Modulating optical appearance

Products that improve the optical appearance of the skin are designed to address the fact that, as the skin ages, the color becomes more irregular as the distribution of brown, red and yellow colors from melanin, hemoglobin and collagen, respectively, becomes more heterogeneous.

Products in this category may work via several mechanisms. They may contain iron oxides that create a temporary tinted layer on top of the skin surface, dihydroxyacetone that works as a progressive self-tanning ingredient to create a semipermanent stain by inducing production of melaninoidins, or minerals (ground mica) that reflect light from the skin surface.

Advanced delivery systems

The oldest cosmeceutical delivery system uses a standard emulsion formulation, typically oil-in-water.

More sophisticated formulations contain liposomes, which are vesicles encasing dissolved active ingredients. When applied to the skin surface, the vesicles open and release their ingredients.

At an even more advanced level, there are multilamellar vesicle emulsions comprised of multilayer spheres that act in a time-release fashion. The sphere shells are composed of phospholipids and as each disintegrates, active agents are delivered to the skin surface.

Nanoemulsions and nanoparticles represent the latest formulation advance. Products using this technology can deliver ultrasmall particles that can penetrate the skin to deliver moisture in the stratum corneum.

Disclosure: Dr. Draelos receives research grants and is an investigator for a number of companies that produce dermatologic and skincare products.

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