Lipids and their Role in Cosmetics
It seems no matter where I look today, hot on the heels of the anti-oxidant craze is the lipid craze. Truly, whether it's in the supermarket or on the Internet, virtually every product I see is supposedly infused with lipids. The other day when I was taking my son into the Good Year dealer for some new tires, I really half-expected to see, "Get the new and improved infused with lipids for greater tread life!". So I thought it would be a great idea to explain just what lipids are, how the help form a barrier and how they affect the suppleness of the skin.

First off, do I recommend lipid-infused cosmetics to my celebrity clients? Absolutely and this is why. When you look at the structure of skin cells toward the surface, you'll notice that they look like tiny bricks surrounded by mortar and, in fact, that's exactly how skin works. During their lifetime, the skin cells are flattened and pushed up toward the surface of the skin and the fat-like substances that surrounds them and which forms the mortar in between them are actually lipids. Lipids are secreted from the cells themselves and, together with the cells, form the epidermal water barrier at the "stratum corneum" or the uppermost layer of skin. This barrier is called the 'lipid barrier'. But before we discuss the role of the lipid barrier, let's look at the two distinct sources of lipids in the skin, both of which yield lipid compositions that are very different. The two sources of lipids in the skin are Sebaceous lipids (Sebum) and Epidermal lipids

As for sebaceous lipids, the debate rages on as to exactly what role they play. Some scientists say it's an outdated role that we have evolved through while others say its necessary for water retention. No matter what the opinion, one fact remains; during the passage through the sebaceous duct of the sebaceous lipids, the triglycerides which sebaceous lipids contain are enzymatically transformed into free fatty acids. These fatty acids are then incorporated into the lipid barrier of the stratum corneum and help in reducing the evaporative loss of water from skin. Fatty acid deficiencies in skin have been said to in cause dry skin and other skin conditions. But, thankfully, sebum is not the only moisturizing lipid, which brings us to the epidermal lipids.

Epidermal lipids are much more complex than sebaceous lipids. They are synthesized, or at least modified, as a basal skin cell undergoes keratinization and matures into a stratum corneum cell. For a better and simple discussion on this, please see "Skin 101: How Skin Works" in the Cosmetics section of this site. I read it and was amazed and pleased at how much a dedicated makeup artist can know about physiology. You'd be surprised at how many people just take the bottle's word for the benefit of something and never bother to assure that the ingredients aren't detrimental to the skin. Anyway, back on track! During this process, epidermal lipids become mixed with sebaceous lipids to compose what is referred to as the "Intercellular Lipid Matrix" in the lower layers of skin and "Lipid Barrier" in the stratum corneum or the surface of the skin. To steal Ms. Facemire's analogy in Skin 101, think "Brick Wall" and you understand how lipids play a role in the skin game.

Lipids, unfortunately, are not immune to the environment. When in contact with sunlight and specifically UV light, or regular old air, lipids undergo what is known as peroxidation. Gaps occur in the lipid matrix, the barrier is broken and the skin is no longer an impenetrable membrane and you have dry, scaly or even cracked skin. This damage occurs on a daily basis requiring a continuous input of lipids to the skin to maintain an effective lipid barrier. I should also note that soaps and detergents combine with the pollution and sunlight and UV rays in the atmosphere which are pronounced with the depletion of the ozone layer and magnified through airborne, polluting gasses to lead to pronounced loss of lipids from the skin as well which is why cleansing with proper cleansers is vitally important. Also, further damage occurs by moisture loss from the skin cells in the lower layers of the epidermis, which affects the health of these cells. There are two problems here; 1) dehydrated cells function poorly and the immune system of the skin becomes weakened which, from a health standpoint, increases the the risk of infection or other skin diseases increases and 2) from a cosmetic standpoint, skin dryness will occur, more fine lines will appear and wrinkles will become larger and deeper.

Now that you know the importance of the lipid barrier both at the surface of the skin and below it in the maturing cellular structure, you question has to be, "Do cosmetics play a role in the Lipid Barrier?" and the answer, for me, is a "Qualified Yes" and the qualification come via two issues.The topical, "rub-on" skin treatment products must contain certain lipids that will be incorporated into the intercellular lipid matrix and lipid barrier to assist in repairing the matrix and barrier AND it must increase the moisture binding properties of skin, reduce water loss and improve the health of the skin.

In my own research into the question, I found several researchers who demonstrated that a mixture of three lipids, cholesterol, palmitic acid and ceramide, repaired the lipid barrier in murine or rat skin where lipid was intentionally removed by the use of acetone. Testing indicated that topical application may be beneficial to people with essential fatty acid deficiency syndrome (EFAD) characterized by skin scaling, hyperproliferation and increased water loss. The symptoms are relieved by linoleic acid applied topically. Other investigators have shown that topically applied lipids can assist in repairing the lipid barrier, if not by directly replacing damaged or lost lipids, then by absorbing into the lipid barrier and exerting their own water barrier properties. Work is continuing to determine which lipids are critical to barrier function and what is the correct 'lipid mix' that one should incorporate into a cosmetic product to assist the lipid barrier in its job. The bottom line is that, for my money, the need for an intact, healthy and functional lipid barrier is critical for the purposes of maintaining the health of the skin on the inside and to maximize the skin's youthful appearance on the outside. Topically applying the correct lipids will assist in maintaining the structure of the lipid barrier and improving the health and beauty of the skin.