The stratum corneum is the outer-most layer of the skin that provides a barrier against internal water loss and the absorption of potentially hazardous materials from the environment. Its structure has been compared to a xe2x80x9cbrick and mortarxe2x80x9d system where skin cells (bricks) are imbedded in a complex mixture of lipids (mortar). Disruption of either of these two components can lead to the impairment of skin barrier function.
Enzymes commonly found in biological fluids, particularly proteases and lipases, are known to damage skin barrier function and cause skin inflammation. For example, prolonged exposure of the skin to fecal proteases and lipases is thought to be a major cause of skin damage that leads to diaper dermatitis in infants. The care of skin in individuals with ostomies is difficult due to the frequent contact of digestive enzymes with skin surrounding the ostomy. These enzymes can degrade skin proteins and lipids and cause irritation of the skin.
Compositions and/or materials or articles that reduce the action of these enzymes on skin will allow for enhanced skin health and the prevention of inflammatory skin diseases such as diaper dermatitis.
There are several approaches known in the art for inhibiting the action of fecal enzymes on skin. WO 99/45974 discloses the use of protease inhibitors in absorbent articles in preventing diaper dermatitis. Inhibitors are defined in this reference as any substance that inhibits the activity of proteases in seven in vitro assays against defined substrates. These inhibitors are required to meet at least one of seven criteria for IC50 (the concentration that inhibits 50% of the enzyme activity) and to reversibly or irreversibly inhibit the hydrolytic action of one or more proteases. WO 99/26610 discloses the use of lipase inhibitors in absorbent articles in preventing diaper dermatitis. These above-mentioned approaches to inhibiting the action of digestive enzymes on skin are limited in that diffusion of the inhibitors into the skin may cause adverse effects by inhibiting endogenous enzymes that are important to normal skin function. For example, it is known that topical application of cholesterol sulfate, a potent serine protease inhibitor, inhibits skin proteases that are responsible for normal desquamation (J. Invest. Dermatol. 111:189-193, 1998). Abnormally dry, or xerotic, skin may arise from topical treatment with protease inhibitors that are able to diffuse into the skin. Thus, what are needed are substances that do not penetrate the surface of the skin and prevent the degradative action of exogenous enzymes, such as fecal enzymes, on proteins within the skin. WO 99/46316 discloses the creation of polymeric inhibitors to inhibit fecal protease-mediated skin irritation. These polymers purportedly do not penetrate the skin surface but still exert their action by directly inhibiting the activity of the enzymes against other substrates.
Compositions that adsorb and inactivate fecal enzymes and thereby prevent them from penetrating into the skin have been disclosed. PCT publication WO 97/38735 and U.S. Pat. No. 5,869,033 teach the use of organophilic clays, such as activated quarternium-18 bentonite, to absorb and deactivate fecal proteolytic enzymes to purportedly prevent diaper rash. These clays are created by modification of well-known clays with long-chain organic amphiphilic compounds, such as long-chain quaternary armines. A diaper fabric incorporating the organophilic clay or a diaper containing organophilic clay dispersed in a superabsorbent polymer is suggested. The ability of unmodified clays to adsorb fecal enzymes was not described. The organophilic clays were incorporated into various pharmaceutically suitable vehicles, such as lotions, emulsions, creams, gels, and other aqueous vehicles. The vehicle, however, must be inert with respect to the organophilic clay and therefore be devoid of substances that bind to the clay and inactivate its ability to bind fecal enzymes. In particular, substances with hydrocarbon chains of C-8 and longer should be excluded from the composition. This restriction limits the inclusion of lipophilic skin health benefit agents that may, for example, enhance skin barrier function, moisturize and/or nourish the skin.
Various lipophilic compositions have been described for the prevention of diaper rash. Typically, barrier creams, lotions or ointments that contain these lipophilic skin health benefit agents are used to provide a barrier on the skin and treat skin conditions such as diaper rash. Typical lipophilic skin health benefit agents include petrolatum, mineral oil, natural oils and fatty acids. While these compositions can enhance the barrier properties of the skin, in many instances the application of these chemistries to the skin can be messy and inconvenient. They are also typically used only when signs of diaper rash are visually present.
Diaper liners may be treated with lipophilic skin health benefit agents, such as petrolatum, which can be transferred to the skin through normal diapering practices. Once transferred to the skin, diaper liner formulations may provide a barrier against feces and urine. These formulations may require high concentrations of petrolatum to ensure sufficient transfer to the skin for a health benefit. High concentrations of petrolatum can be messy, greasy to the touch, and may impair the fluid handling properties of an absorbent article, such as a diaper. The slow penetration of petrolatum into the skin can lead to smearing of the agent over the skin and onto clothes and other materials.
Based on the above-mentioned limitations, compositions are needed that adsorb irritants in biological fluids, such as fecal enzymes, and are compatible with lipophilic compositions that may improve skin health by other mechanisms. None of the above mentioned approaches to preventing diaper rash have explored the combination of lipophilic chemistries with particulate agents to adsorb enzymes and thus prevent skin inflammation, such as diaper dermatitis. Furthermore, the ability of unmodified clay particles to bind fecal enzymes has not previously been described.
The present invention provides that lipophilic chemistries and particulate skin irritant sequestering agents, such as non-organophilically modified clays, work synergistically to provide superior enzyme binding characteristics, and thus prevent damage to skin. These compositions can be used as superior diaper rash preventing agents and their incorporation into absorbent articles, such as diapers, allows for transfer of the beneficial agents to the skin.
Therefore, the present invention provides methods of using absorbent personal care articles, such diapers and adult incontinent briefs, comprising an absorbent article and having disposed thereon a skin irritant sequestering effective amount of non-organophilically modified particulate skin irritant sequestering agent and a lipophilic skin health benefit agent.
The present invention provides that the combination of particulate skin irritant sequestering agents and lipophilic skin health benefit agents provides a superior ability to adsorb, or sequester, irritants in biological materials, such as fecal enzymes, and prevent inflammatory skin diseases caused by said irritants, such as diaper dermatitis. The adsorption, or sequestration, of these irritants prevents their penetration into the skin where they cause skin damage and inflammation. A composition suitable for practicing the method of this invention comprises a skin irritant sequestering effective amount of a non-organophilically modified clay, such as bentonite or laponite, in combination with a lipophilic skin health benefit agent, such as petrolatum.
In a further embodiment of the invention, particulate sequestering agents in combination with various lipophilic skin health benefit agents demonstrate a synergistic effect. Lipophilic skin health benefit agents include petrolatum, steric acid, isoparrafins, various emollients, sterols, fatty acids, triglycerides and waxes, for example. A further embodiment of the method of this invention includes using absorbent articles wherein said compositions are incorporated on the body facing material of disposable absorbent articles, such as diapers, training pants, adult incontinent products, underpants, feminine care products and the like.