Skin dryness is one cause of barrier breakdown. Dermatologist Loretta Ciraldo, MD,  CEO of CosMedical Technologies in Miami, says the skin barrier also serves as a moisture-retention agent. "The skin is about 80% water. Since the environments we live in are much drier, our skin is always trying to maintain water balance," she notes.

"When you talk about the barrier, you really should be talking about glycolipids and ceramides contained in the structure of the barrier, which is the outermost part of the stratum corneum," continues Dr. Ciraldo. "In between the dead cells and cellular debris is the lipid content, the chemical and organic compounds that reproduce the barrier function."

Aging is another cause of skin barrier breakdown, notes Daniel Yarosh, PhD, president

and chairman of AGI Dermatics, Freeport, New York, because the skin reduces roduction of ceramides and glycolipids, key components in the skin barrier.

One of the ironies in trying to maintain healthy skin and an attractive appearance is using antiaging regimens that strip the skin of natural lipid content. We need to advise patients to take care when exfoliating, advises Dr. Ciraldo. "This gets rid of dead cells, but it also gets rid of lipids, causing dry skin."

A proper ratio of ceramides, cholesterol, and free fatty acids must be present in the layers of lipid to achieve an optimal effect, says Dr. Thornfeldt. "The ratio that activates the repair process of the damaged barrier should be three parts of either cholesterol or ceramides and one part of the remaining two, of which half of the fatty acid component must be linoleic acid." He adds that disruption of the barrier activates chronic inflammation, which can inhibit collagen and elastin production and destroy supporting tissues as well as damage pigment and skin cells, predisposing them to premalignant deterioration and disease.

Dr. Ciraldo thinks the overuse of exfoliating agents like Retin-A and retinol, derivatives of vitamin A, are major causes of impaired barrier function. "I treat women who come in with very dry, wrinkled skin, especially around the eyes where the skin is thin," explains Dr. Ciraldo. "Applying a potent retinol like Retin-A nightly only exaggerates crow's feet."

Dr. Ciraldo emphasizes products with a combination of glycolipids and ceramides. "The formulation for CosMedical Lipid Drops is produced via bio-fermentation techniques to recreate bio-identical skin lipids," she explains. "When applied topically, these large molecules sit on the surface of the skin between the dead cells of the stratum corneum, so the applied lipids will help restore the skin barrier function. Independent clinical testing has shown that this product provides sustained moisturization for six hours after application and diminishes the appearance of fine lines."