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Pharmaceutical companies and cosmetic companies are promoting cosmeceuticals for treating dry skin, but very few scientific studies have been published to validate the claims made. Changes are made to increase the hydrophobicity and occlusive properties of formulations, but are these products any more effective than the present gold standard, petrolatum? Lipids may be absorbed but what effect does this have on structural components in the skin? Cell kinetics are probably more important than is generally understood. In diseases such as psoriasis, the turnover of cells can be much higher than in normal skin, preventing homeostatic mechanisms from maintaining an effective barrier. Possibly, local occlusion slows down cell turnover and allows the skin to repair itself.2
Repair of the Cutaneous Permeability Barrier
When the integrity of the cutaneous permeability barrier is perturbed, a homeostatic repair mechanism is stimulated that causes the rapid repair of barrier function. It has recently been suggested that barrier disruption stimulates the expression of amphiregulin and nerve growth factor and that these regulators of keratinocyte growth and differentiation may be responsible for the increased proliferative response that is associated with barrier disruption.3
New compounds and new delivery systems for treating dry skin are under development. Dr. Peter Elias and his associates in San Francisco and at Cellegy Pharmaceuticals have been collaborating in the development of lipid mixtures for the skin. Their product Glylorin (monolaurin), which has just been licensed to Glaxo Wellcome, entered phase III clinical trials in January 1996 for non-bullous congenital ichthyosiform erythroderma (n-CIE). Its mode of action is unclear, but in phase II studies it exhibited surfactant, antimicrobial, anti-inflammatory, and anti-proliferative properties.
Practical Advice on Treating Dry Skin4
Dry skin becomes less irritable with emollient therapy, which should be considered as an adjunctive treatment for a wide range of itchy dermatoses. Emollients can serve as topical corticosteroid-sparing agents in diseases such as psoriasis, atopic hand dermatitis, and winter itch, and may also be used by those who are exposed to primary irritants in the home or workplace.
Preferred Agents and Reasons
Ask patients what they currently use. If this is an acceptable product, urge continued vigorous compliance.4
The length of time an application of emollient provides benefit varies with factors such as the time of season, patient occupation, and preparation used. Many patients have individual preferences that should be taken into account in choosing an emollient.4 Patients may respond well to Lac-Hydrin® or Lacticare® or traditional formulations such as Cetaphil®, Neutrogena Norwegian Formula Hand Cream,® or Vaseline Intensive Care Lotion® - Editor. Some patients prefer cosmetic elegance, some strong fragrance, whereas others are satisfied with petrolatum - an excellent agent but the antithesis of elegance.4 Products from reputable commercial companies are those that are most likely to deliver what they promise.4
Have We Improved on Petrolatum?
In the past, petrolatum was assumed to be occlusive, blocking transcutaneous water loss and trapping water under the skin's surface. In human volunteers, studies of barrier recovery following acetone-induced barrier disruption, plus tracer and staining studies have shown that petrolatum neither forms nor acts like an epicutaneous impermeable membrane. Petrolatum permeated through the stratum corneum interstices, allowing normal barrier recovery despite its occlusive properties.5
Lipids in emollients help restore the normal barrier function of the skin and protect it from outside influences. Lipids also retard transepidermal water loss and allow more complete hydration of the skin. They also play an anti-inflammatory role in the skin. Humectants bind water and thus attract water to the skin and temporarily hold it there. The role of other ingredients such as urea and alpha hydroxy acids is incompletely understood, but expanding. These latter agents likely enhance the activity of the emollients.4
Avoiding Side Effects4
Avoidance of side effects is best accomplished by suggesting fragrance and dye-free agents from reputable companies. When applying agents with high alcohol concentrations, burning sensations may trouble patients with extremely irritated skin. Thus, the initial use of less irritating products can help. Once the skin has its barrier function restored, lotions that were previously irritating may be tolerated.
Routinely recommend the use of emollients on a repeated basis. Patients sometimes need to hear more than once that they need to use these products. Men in particular may be reluctant to use emollients, but should be directed to do so. Professor Fleischer tells patients with asteatotic dermatitis of the legs: "We can make this go away, but without prevention it is guaranteed to come back."4
Best Technique for Application4
Apply immediately after tepid bathing and patting dry with a towel. Application can be repeated again during the day. For patients with hand dermatitis, urge them to keep containers of their favorite emollient at their desk, in their car, and at every sink in their house. To paraphrase Louis XIV, "out of site, out of mind." Use of emollients must be convenient.4
How can the Effect of Emollients be Prolonged?
Products with higher concentrations of lipids are valuable for prolonging the emollient effect. The thickness of a lotion or cream may be deceiving, since thickening agents may have been added so that products can remain elegant. With emollients there is no free lunch. The more lipid, the better the therapeutic effect and the worse the elegance. The less lipid, the better the elegance, and the worse the therapeutic effect.4
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