Cholesterol has a negative image among many people given the unhealthy nature of dietary cholesterol. But cholesterol is made by all of our cells, and it is an important component in the skin’s barrier. Let’s quickly look at why cholesterol is successfully used in skin care products.

As the outermost layer of the epidermis, the stratum corneum serves as an important barrier. It is composed of terminally differentiated (fully matured cells), anucleated corneocytes that are derived from keratinocytes, that reside within a lipid matrix. Together, the corneocytes and lipid matrix comprise the “bricks and mortar” structure of the stratum corneum. When combined with ceramides and free fatty acids, cholesterol forms the lipid mortar between the dead corneocytes, forming a water-impermeable barrier that prevents evaporative water loss. This structure, along with other structures such as tight junctions in the epidermis, create a barrier to external insults from pathogens, allergens, and toxins. Cholesterol reaches its highest concentration in the granular layer of the epidermis, just under the stratum corneum.

Cholesterol used in topical products is usually of vegetable origin, primarily derived from squalene. It is safe and effective (when used with free fatty acids and ceramide) as a topically applied product. That is, complete mixtures of ceramide, free fatty acid, and cholesterol facilitate normal barrier function when applied topically. However, incomplete mixtures of these lipids produce abnormal lamellar bodies, the critical organelles that regulate the formation and maintenance of the skin barrier. This leads to an abnormal stratum corneum. In other words, unless you use the complete mixture of lipids; ceramide, cholesterol, and free fatty acids, the barrier function of the stratum corneum will not be optimal. This is why I formulated Neogenesis’ Barrier Renewal Cream to contain the complete set of lipids, including cholesterol, ceramide, and free fatty acids, necessary for optimally building the stratum corneum.

Many people ask, what are these three lipids; cholesterol, ceramide and free fatty acids?

Lipids are fatty, waxy, or oily compounds that are soluble in organic solvents and insoluble in polar solvents such as water. Lipids include:

• Fats and oils (triglycerides)
• Phospholipids
• Waxes
• Steroids

Lipids that are important to our discussion of skin and human cells include fats and oils (triglycerides or triacyglycerols), fatty acids, phospholipids, and cholesterol. Cholesterol and plant sterols, such as sitosterol, are high-molecular-weight alcohols with a characteristic cyclic nucleus. Fatty acids generally consist of a straight alkyl chain, terminating with a carboxyl group. Ceramides belong to the sphingolipids. Their structure consists of a hydrocarbon chain termed long-chain base, such as sphingosine or phytosphingosine. One fatty acid is linked to the ceramide. In this case, the fatty acid is not “free,” rather it is a component of the ceramide. The free fatty acids are not linked to the ceramide.

The bottom line: The biochemistry of lipids in the body, including the skin, is complex. Just remember the three lipid types that are critical to building normal barrier function, namely, cholesterol, ceramide, and free fatty acids. If you want to delve into the complexity of lipid biochemistry in the skin, a set of excellent research and review papers are found here.