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Allantoin-containing skin cream

Allantoin-containing skin cream description/claims

This application is a continuation-in-part application of application Ser. No. 09/758,781, entitled “Allantoin-Containing Skin Cream,” filed Jan. 11, 2001 by Elliott Farber, which in turn was a continuation-in-part application of Ser. No. 09/570,266, entitled “Allantoin-Containing Skin Cream,” filed May 12, 2000 by Elliott Farber, which in turn is a continuation-in-part application of application Ser. No. 09/360,095, entitled “Oil-in-Water Emulsion With Improved Stability,” filed Jul. 23, 1999 by Elliott Farber, now U.S. Pat. No. 6,281,236, issued Aug. 28, 2001. All three of these prior applications are hereby incorporated in their entirety by this reference.

1. Field of the Invention

This invention is directed to a skin cream containing allantoin in an oil-in-water emulsion with improved stability.

2. General Background and State of the Art

Allantoin is a commonly used ingredient in cosmetic applications, particularly for skin creams, where it exerts a skin protective function. Many such cosmetic compositions and other compositions are prepared as emulsions, particularly oil-in-water emulsions. One emulsifier system used with such compositions is a combination of sodium lauryl sulfate and beeswax. Although solutions of sodium lauryl sulfate are alkaline with an approximate pH of 9.5, the simultaneous use of beeswax with its organic acids produces a complex and neutralized system with a pH of about 6.8 to about 7.5. However, in such a system with a pH range of 6.8 to 7.5, allantoin degrades significantly with time and in accelerated stability tests at 40° C. Because cosmetics and other preparations designed for application to the skin are typically stored by users at room temperature, and room temperatures can fluctuate with climatic conditions, such a degree of stability is undesirable. Therefore, there is a need for an oil-in-water emulsified composition containing allantoin in which the stability of allantoin is increased.

In particular, there is a need for compositions that are suitable for treating a number of severe and difficult-to-treat skin conditions. One of these skin conditions is epidermolysis bullosa. This is a severe genetic skin disorder in which the skin breaks down and large blisters appear. These blisters are difficult to treat by conventional means. Other skin diseases for which improved treatments are needed are pressure ulcers, decubitus ulcers or bed sores, and diabetic ulcers, and milia, as well as other conditions affecting the skin and having an inflammatory component such as eczema, urticaria, atopic dermatitis, contact dermatitis, arthritis, gout, and lupus erythematosus. Therefore, improved compositions that are suitable for treating these diseases are needed.

In general, a composition according to the present invention comprises an oil-in-water emulsion comprising:

(1) allantoin; and

(2) at least one anionic or nonionic emulsifier that is substantially hydrophilic and is soluble in water.

The pH of the composition is in a range of from about 3.0 to about 6.0. This pH range stabilizes the allantoin and makes storage of the composition for extended periods practical. Preferably, the pH of the composition is in a range of from about 5.0 to about 6.0.

Typically, the at least one anionic or nonionic emulsifier is selected from the group consisting of:

(1) an acidic anionic polymer,

(2) an anionic emulsifier selected from the group consisting of ammonium lauryl sulfate, sodium laureth sulfate, sodium oleyl succinate, ammonium lauryl sulfosuccinate, sodium dodecylbenzenesulfonate, ammonium laureth sulfate, sodium N-lauryl sarcosinate, and sodium lauryl sulfate;

(3) a nonionic emulsifier that is an ethoxylated ether or an ethoxylated ester whose chain length ranges from 8 to 22 carbon atoms;

(4) glyceryl stearate;

(5) cetyl alcohol;

(6) stearic acid;

(7) sodium stearoyl lactylate;

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