DE68914455T2 - Waterproof sunscreen. - Google Patents

Description

The present invention relates generally to a skin protectant having improved water repellency and, more particularly, to a new and improved formulation comprising aliphatic waxes and anhydrous hydrophobic starch in a pharmacologically acceptable anhydrous carrier which, when mixed with a sunscreen and applied topically to exposed human skin, is surprisingly capable of not only blocking UV radiation from the skin but also of making the surface of the skin water resistant without making it sticky. The composition has been widely accepted by users and significantly reduces skin damage that would otherwise occur when exposed to such solar radiation. The subject skin protectant is also capable of preventing and controlling diaper rashes and similar skin irritations resulting from unwanted accumulation of urine or similar skin-unfriendly solutions on human skin.

Although the need to protect human skin against solar radiation, especially UV radiation, has been well established over the past two decades and a variety of formulations with varying degrees of "filtering" or "blocking" have been developed, it has been shown that the benefits of such agents are quickly lost when the user sweats or enjoys water games, and the protective coating is then washed off with rapid loss of the benefits.

The need for a protective coating on the skin is of crucial importance since it is now well established that sunlight contributes to aging and carcinogenesis by exacerbating UV injury, altering the vascular system, producing diffusible intermediaries, altering histone binding properties and/or damaging DNA repair processes (see Kaidbey et al. in Arch. Dermatol.", 1982, 118 (5):3155-318).

UV light and heat have been shown to synergistically denature human oral squamous mucosa DNA. This work was carried out at 24ºC and 32ºC (corresponding to the skin surface temperature indoors) and 42ºC (corresponding to the skin surface temperature in bright sunlight at 26ºN latitude) (see Roth and London in "J. Invest. Dermatol.", 1977, 69, 368-372). Roth and coworkers showed a positive linear relationship between DNA denaturation and irradiation temperature.

Principal considerations for selecting effective sunscreens are burns, tanning and chronic changes such as cancer, elastic tissue degeneration, wrinkling and pigmentation. However, when the need for protection through waterproofing is taken into account, there is little information. Available sunscreens may provide protection against UVB and UVA radiation, but unfortunately they are usually not "skin-proof" and can be easily washed off by water or sweat. This leads to many commercial sunscreens giving users a false sense of security.

In an attempt to address this problem, various products containing a sunscreen and a water-repellent agent in a cream or lotion base have been brought to market. However, insofar as they are intended to impart certain desirable properties to the skin, in particular cosmetic properties, these products still leave much to be desired. They usually do not have the feel or the appearance of conventional cosmetic creams or lotions for other purposes and are usually very sticky and give the user an unpleasant feeling. This sticky feeling is usually mediated by the polymer contained in the sunscreen as a water-repellent agent. Consequently, the usual attempts have only consisted of using these plasticizers in cream/lotion bases, without paying attention to the formulation of the cream/lotion base itself.

The use of such polymers has other disadvantages. These include a "powdery" appearance due to excessive friability, which further contributes to poor "strength". Both cationic and anionic polymers can cause this problem. Similar considerations also apply when evaluating substances to be applied to children's skin to prevent so-called diaper rash.

GB-1 277 324 describes a solid Vaseline preparation with hydrophobic starch to reduce the "greasiness" of the Vaseline on the skin.

There is therefore a real need in industry for a waterproofing composition or preparation with particular suitability for sunscreens or in the treatment of fluid-induced dermatological irritations. The preparation or composition in question should provide effective and stable protection for human skin of a level of permanent integrity previously unattainable using anionic or cationic polymers for waterproofing. This is the task to which the present invention is dedicated.

The present invention is based on the surprising discovery of a new and unique formulation containing synthetic aliphatic waxes and anhydrous hydrophobic starch in an anhydrous base which can later be mixed with any formulation of conventional ultraviolet (UV) absorbents or other topically applicable medicaments. When used with sunscreen reagents and similar additives and then applied to mammalian skin, the formulation most unexpectedly renders the skin waterproof while simultaneously preventing sun rays, urine and other "nuisances" from entering the skin. In this way, it protects the skin against the massive damaging effects of such "nuisances" regardless of the activities of the user.

In particular, the present invention is based on the finding that a sunscreen or a therapeutic agent can be produced without the use of polymers by means of a a unique combination of synthetic aliphatic waxes and anhydrous hydrophobic starches housed in an anhydrous carrier, such as mineral oil and/or aliphatic esters.

When used in a topical application, this new preparation has numerous advantages including the creation of a water barrier, effective water repellency, strong resistance to washing off, physiological inertness, non-irritation and good stability, as well as an elegant silky feel without stickiness.

In principle, this invention wanted to use the aforementioned advantages in the formulation of a sunscreen base that was even more waterproof than the relevant preparations available to date. In particular, the invention ensures improved sun protection through superior water repellency, longer lasting protective effect and a more elegant, silky feel on the skin than is the case with all products available to date on the market.

A main object of the present invention is therefore to create, without the use of sticky polymeric materials, a new and improved preparation with synthetic aliphatic waxes (for example SYNCROWAX from Croda, Inc., New York) and anhydrous hydrophobic starch (for example DRY FLO from National Starch and Chemicals Co., Bridgewater, N.J.) which, after topical application to human skin, has such a waterproofing or water-repellent effect that active, previously selected reagents or aids remain in effective relationship with the skin over a longer period of time and the skin damage that otherwise occurs with long-term exposure to harmful influences as a result of rapid washing off of the protective substance and lack of protection of the skin surface is reduced.

Another object of the present invention is to provide a new and improved topically applicable water-repellent sunscreen which is non-toxic, easy to apply and cosmetically is acceptable, does not affect clothing in contact with it and shows an unexpected tendency to protect mammalian skin from the harmful effects of solar radiation.

A further object of the present invention is to provide a new and improved, topically applicable, waterproof skin protection base which is compatible with conventional UV-A and UV-B sun protection reagents and can be easily mixed with them to form a new multi-faceted product for long-term protection against solar radiation, even when the user is engaged in water sports.

Finally, it is also an object of the present invention to develop methods for protecting the skin of humans and similarly susceptible animals from the harmful effects of exposure to solar radiation, urine and similar "nuisances" by preventing premature removal when it comes into contact with water and similar solvents, excluding treatments on the human body in accordance with Article 52(4) EPC.

These and other objects, as will become apparent below, can be achieved by the present invention in a quite unexpected manner. This will become apparent in particular from the following detailed description of an exemplary embodiment thereof.

The present invention relates to a skin protectant for long-term topical application to the skin of humans and similarly susceptible animals (hereinafter referred to as "mammals") with the unexpected ability to prevent solar radiation from damaging the skin and causing cancer. The base of the invention is not only compatible with the usual reagents for blocking and filtering solar radiation, but also provides an unexpected degree of water repellency. In this way, it protects the active reagents against premature removal due to exposure to water. This aspect enables the same base to effectively protect delicate infant skin against the ravages of diaper rash.

The key to the present invention is a A base composition which not only provides a compatible carrier for most accepted sunscreens and blockers, but when applied topically to human skin forms a water-resistant coating or film thereon and retains its effective position even when the user sweats excessively or jumps in and out of the water during a trip to the sea, lake, pond, swimming pool, etc. Similarly, the coating will remain at the application site when applied in the presence of a large quantity of urine.

The present invention relates to a preparation for waterproofing mammalian skin comprising, in % by weight, 1-10% of a C₁₈-C₃₆ saturated synthetic fatty acid wax, 3-30% anhydrous hydrophobic starch, dispersed in 60-96% of a pharmacologically acceptable anhydrous carrier.

The key ingredients of the preparation according to the invention are in particular a synthetic aliphatic wax, i.e. a high molecular weight C₁₈-C₃₆ saturated synthetic fatty acid wax such as SYNCROWAX or an equivalent synthetic wax developed for use in cosmetics, which is mixed with an anhydrous hydrophobic starch, e.g. aluminum starch octenyl succinate (sold as "DRY FLO").

The anhydrous hydrophobic starches have proven to be extremely resistant to wetting with water while maintaining the ability of starch to absorb moisture without swelling.

In combination with the synthetic waxes described above, such as SYNCROWAX, a preparation is obtained that unexpectedly has far better film-forming and water-barrier properties than the polymers previously used as waterproofing agents. Furthermore, there is no flaking or leaching of the film or the additives on it, such as sunscreen. Another advantage is the unexpected (wash-off) resistance of the film to sweat, urine, water and the like.

The basic combination of the present invention consists of an aliphatic synthetic wax and an anhydrous hydrophobic starch, for example SYNCROWAX and DRY FLO, as essential components, which are housed in a pharmacologically acceptable, anhydrous extender which enables the compositions in question to be applied to the skin. Then - as will be described - conventional UV filters or absorbents or other previously selected topically active medicaments are mixed in. The resulting preparations can be in solid or liquid form. The masses or preparations according to the invention can also contain a wide variety of cosmetic and personal care products, such as hand and body lotions, ointments, lip balm, facial cosmetics, diaper creams, ostomy creams and the like.

The amount of C₁₈₋₃-C₃₆ saturated synthetic fatty acid wax and anhydrous hydrophobic starch contained in the anhydrous base can vary greatly. The amount of the synthetic aliphatic wax is in the range of 1 - 10 wt.% of the total preparation. The anhydrous hydrophobic starch varies from 3 - 30 wt.%.

According to a preferred embodiment, one or more other agents, such as conventional UV-A and UV-B absorbents, opacifying agents such as titanium, zinc or iron (III) oxide and the like, can be added to the base mass. Larger amounts of these agents can be incorporated into a wide variety of products, the limits of which are set only by processing and economic considerations and by the desired filter effect. When used, the amount of UV-A and UV-B absorbents is preferably up to 20% by weight of the preparation.

Other agents or ingredients which can be used as an anhydrous extender to replace the above-mentioned mineral or vegetable oils for the basic preparations according to the invention are lanolin, vaseline, glycerin, triglycerides of fatty acids, polyethylene glycols, oxyethylenated fatty alcohols, esters such as isopropyl palmitate, myristate and stearate, silicone oils, oleyl oleate and butyl stearate, animal oils, fatty alcohols, glycerin monostearate and organic and mineral waxes. These other ingredients are usually used in an amount of 10 - 96% by weight of the total formulation.

Examples of cosmetic ingredients that can be used in a preparation according to the invention are thickeners, plasticizers, superfatting agents, emollients, as well as preservatives, silicones, perfumes or other compatible ingredients that are usually used in cosmetics.

If product design considerations require their use, the following film-forming agents, polymers and cosmetic resins can be used: polyvinylpyrrolidone, vinylpyrrolidone/vinyl acetate copolymers with monomer ratios of 70/30 to 30/70, vinyl acetate/unsaturated carboxylic acid copolymers, e.g. a copolymer with 90% vinyl acetate and 10% crotonic acid, methyl methacrylate/stearyl methacrylate/dimethylaminoethyl methacrylate terpolymers, fully quaternized with dimethyl sulfate, the monomers being present in particular in a ratio of 20/23/57, and a vinyl acetate/allyl stearate/allyloxyacetic acid terpolymer, in particular in a ratio of 80/15/5, maleic anhydride/methyl vinyl ether copolymers, e.g. the commercial products "Gantrez AN" as well as the ethyl, isopropyl and butyl esters of these copolymers and maleic anhydride/butyl vinyl ether copolymers. Of course, these polymers, which impart a sticky or tacky feel in conventional cream/lotion bases, are smooth and silky when used in accordance with the invention.

For topical use, sunscreens must be non-toxic and non-irritating to skin tissue and must form a uniform, continuous film on the skin when applied. In addition, the active sunscreens must be chemically stable and, in particular, when present on the skin, resistant to chemical degradation and photodegradation as well as to absorption through the skin. Sunscreens that absorb UV radiation and are suitable according to the invention are:

Oxybenzone (2-hydroxy-4-methoxybenzophenone); Dioxybenzone (2,2'-dihydroxy-4-methoxybenzophenone); aminobenzoic acid; Cinoxate (2- ethoxyethyl p-methoxycinnamate); Diethanolamine p-methoxycinnamate; digalloyl trioleate; Ethyl 4-bis(hydroxypropyl)aminobenzoate; 2-ethylhexyl-, 2-cyano-, 3,3-diphenyl acrylate; Ethylhexyl p-methoxycinnamate; 2-ethylhexyl salicylate; Glyceryl aminobenzoate; Homosalate (3,3,5-trimethylcyclohexylsalicylate); Triethanolamine salicylate; 2-phenylbenzimidazole-5-sulfonic acid; Sulisobenzone (2-hydroxy-4-methoxybenzophenone-5-sulfonic acid); Padimat A (amyl p-dimethylaminobenzoate); Padimat O (octyldimethyl p-aminobenzoate); 4-tert-butyl-4'-methoxydibenzoylmethane; the combination of 2-hydroxy-1,4-naphthoquinone and dihydroxyacetone; and menthylanthranilate.

Each of the compounds mentioned has been used alone or in combination with others in a variety of sunscreens and has been shown to provide different sun protection factors (SPF) when evaluated in standard human solar simulator tests.

A sunscreen agent to be used according to the invention for protection against ultraviolet A (320 - 400 nm) is one from the group of pentyl and 2-ethylhexyl esters of 4-(dimethylamino)benzoic acid, dioxybenzone, ethylhexyl p-methoxycinnamate, ethyl 4-bis(hydroxypropyl)aminobenzoate, 3,3,5-trimethylcyclohexyl salicylate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, 2-ethylhexyl salicylate, 4-tert-butyl-4'-methoxydibenzoylmethane and mixtures thereof. The sunscreen agent is present in amounts of 1.0 - 20.0, preferably 4.0 - 11.0% by weight of the total preparation.

In one embodiment of the invention, a suitably large stainless steel tank is charged with a mineral oil, whereupon the double mixers (the swing arm rotates clockwise at about 10 rpm, the turbine rotates counterclockwise at about 12 rpm) are activated.

The batch is then heated to 110ºC. SYNCROWAX is added while heating (the oscillator runs at 14 rpm, the turbine at 24 rpm) until a complete and homogeneous dispersion is achieved.

While the mixers are rotating at the specified speed, a UV-A absorber, such as benzophenone-3, is introduced and completely dissolved in the batch.

Anhydrous hydrophobic starch (DRY FLO) is then added to the batch while the mixers are switched to higher speed and the temperature is maintained above 78 - 80ºC for 1 hour.

A suitable antioxidant, such as dl-α-tocopherol, and suitable cosmetic additives, such as cyclomethicone and the like, are then incorporated while stirring.

Finally, the batch is cooled at a rate of approximately 0.5ºC/min until a temperature of 25 - 27ºC is reached. The batch is now ready for packaging after approval by quality control.

Preparations according to the invention were produced by carrying out the measures described. Components other than the synthetic aliphatic wax and the anhydrous hydrophobic starch are given as examples below: Component Mineral oil Octyl methoxycinnamate Glyceryl tribehenate and calcium behenate (trade name: SYNCROWAX HRS-C) Benzophenone-3 Cyclomethicone dl-α-tocopherol Anhydrous starch (DRY FLO)

The various preparations according to the invention were applied to human skin and tested for water repellency according to the protocol described in Example 8.

A number of the synthetic waxes used in the examples and defined by the trade name SYNCROWAX have proven to be particularly suitable for the present invention. All of these waxes are based on a C₁₈-C₃₆ saturated synthetic fatty acid wax. They exhibit properties, eg thermoplastic/crystalline properties, which are similar to those of natural waxes. The synthetic waxes used in the present case are "HRS-C" (glyceryl tribehenate and calcium behenate), "ERL-C" (ethylene glycol ester of a C₁₈-C₃₆ waxy fatty acid) and "HGL-C" (glyceride esters of C₁₈-C₃₆ waxy fatty acids) (cf. CTFA Cosmetic Ingredient Dictionary, 3rd edition, The Cosmetic, Textile and Fragrance Association, Inc., Washington, DC 20005).

The following non-limiting examples are intended to illustrate the present invention in more detail.

example 1

Mineral oil is poured into a suitable sized vessel heated to 110ºC and mixed thoroughly. The synthetic aliphatic wax is then added to the mineral oil and mixed with it until a uniform consistency and mass is formed. At this point, the desired UV blocker is added to the existing mixture. After thoroughly mixing and maintaining a temperature above 70 - 80ºC, the anhydrous hydrophobic starch is added with continued stirring. Finally, if required, any additives such as antioxidants, cosmetic additives and the like are added and thoroughly incorporated into the mixture.

The mixing time and temperature and the number of phases are of course dictated by the materials used. The entire mixing process is carried out in the usual manner.

Example 2

A waterproof sunblock having the following weight percentage composition is prepared in the manner described in Example 1:

Mineral oil 18.5 - 89.9

Anhydrous starch 3 - 30

Isopropyl palmitate 1 - 20

PEG-7 Glyceryl Cocoate 1 - 5

Cetearyl isononanoate 1 - 5

Octylmethoxycinnamate 1 - 7.5

Benzophenone-3 1 -5

Phenyldimethicone 1 - 3

dl-α-Tocopherol1 0.1 - 1

SYNCROWAX HRS-C 1 - 5

Example 3

Preparations according to the invention were prepared by carrying out the steps of Example 1 using a combination of synthetic waxes specified below. Other blockers such as TiO₂ and mica with decreasing stickiness can be used. Ingredient Mineral Oil Octyl Methoxycinnamate SYNCROWAX HRS-C Mica Titanium Dioxide Anhydrous Starch Benzophenone-3 Cyclomethicone dl-α-Tocopherol SYNCROWAX HGL-C SYNCROWAX ERL-C

Example 4

Following the steps of Example 1, an anhydrous transparent sunblock was prepared with the following formulation:

2-Ethylhexyll stearate 10 - 17

Mineral oil 42.9 - 81

SYNCROWAX HRS-C 3 - 8

Lanolin 1 - 5

Anhydrous starch 1 - 5

Silicon dioxide 1 - 8

Silicone oil 0.5 - 5

dl-α-Tocopherol 0.5 - 4

Octyl methoxycinnamate 1 - 7.5 Benzophenone-3 1 - 5 Oleyl alcohol 1 - 3

Example 5

By carrying out the measures described in Example 1, a waterproof hand cream without sunscreen was produced with the following weight percentage formulation:

Mineral oil 44.0 - 85.50

C12-15 alcohol benzoate 5.0 - 20

SYNCROWAX HGL-C 1,0 - 5

dl-α-Tocopherol 0.5 - 1

Anhydrous strength 3.0 - 20

Cyclomethicone 5.0 - 10

Example 6

By carrying out the measures described in Example 1, a waterproof diaper rash cream preparation with the following weight percentage formulation was produced:

C₁₀₋₋₃₀-cholesterol lanosterol 10.0

Anhydrous starch 10.0

Emulsifying wax NF 7.5

Mineral oil 47.5

SYNCROWAX HRS-C 10.0

PVP/Eicosene Copolymer 2.0

dl-α-Tocopherol 2.0

Dimethicone 3.5

Cyclomethicone 7.5

Example 7

By carrying out the measures described in Example 1, a waterproof lip balm containing sunscreen was prepared with the following weight percentage composition:

Mineral oil 7.0

Castor oil 6.0

2-Ethylhexyl stearate 4.4

Oleyl alcohol 8.5

SYNCROWAX HRS-C 7.5

Anhydrous starch 7.5

Dimethicone 2.0

Octylmethoxycinnamate 7.5

Octyl salicylate 5.0

Menthylanthrinolate 5.0

Example 8

By carrying out the measures of Example 1, a sunscreen preparation with the following weight percentage formulation was produced:

Mineral oil 47.3

SYNCROWAX HRS-C 1.5

SYNCROWAX HGL-C 0.5

SYNCROWAX ERL-C 0.5

Stearalkonium hectorite and propylene carbonate 4.0

C₁₂₋₁₅-Alcohol benzoate 9.0

Benzophenone-3 4.2

PEG-7 Glycerin Cocoate 2.0

Cetearyl isononanoate 1.0

Octyl methoxycinnamate 7.4

dl-α-Tocopherol 0.1

Dimethicone 6.0

Silicon dioxide 6.5

Anhydrous starch (DRY FLO) 10.0

Example 9

Tests were conducted in accordance with the requirements and criteria set forth in the Proposed Monograph for OTC Sunscreen Drug Products issued by the F.D.A. on August 25, 1978 (43 Fed. Reg. 166 at 38206-38269).

The purpose of these tests was to determine the sun protection factor (SPF) effectiveness on the skin of humans before and after a total of 40 or 80 minutes of immersion in water.

The wet control test material, Johnson & Johnson, SUNDOWN moderate (SPF=4), and the static control, 8% homosalate, were prepared according to FDA regulations (Fed. Reg. Ibid at 38259). The test product was prepared according to Example 8.

The light source was a solar ultraviolet simulator, Model 10S (Fed. Reg., Ibid at 38260) with a 150-watt xenon arc lamp and all necessary optical elements and a regulated power supply.

The test was carried out on a total of 20 light-skinned people (3 male, 17 female, ages 20 to 53) of skin types I, II and III. The test was carried out as follows:

Physical examination determined the presence of sunburn, tanning, scars, active skin lesions, and uneven skin tone on the back area being tested. The presence of moles, blemishes, or birthmarks was acceptable as long as they did not interfere with the test results. Excess hair on the back, if present, was shaved off.

A test site area served as an area for determining the personal minimum erythema dose (MED) after application of the individual sunscreen products or for determining the personal MED of unprotected skin (control site). The personal MED is the exposure time that causes the least noticeable redness 16 - 24 hours after exposure to light.

The test area consisted of the back between the waistline and the shoulder blades and laterally to the midline. The test site areas were horizontal or vertical and were rectangular or square. Each test site area for product application or standard control application was 50 cm². These test sites were outlined with gentian violet. The test subject stood upright.

Each test site area of the test was divided into five sub(test) areas of at least 1 cm². For subjects 1 - 5, three test site areas were provided for the test material, one for the determination before immersion in water and one for the determination after 80 minutes of immersion in water. For subjects 1 - 5, three test site areas were provided for the test material, one for the determination before immersion in water and one for the determination after 80 minutes of immersion in water. 6 - 20, two test site areas were used for the test material and for the wet control, one for the determination before immersion in water and one for the determination after 80 minutes of immersion in water. The location of the test site areas was randomly selected among the 20 subjects. A further test site area was used for the 8% HMS SPF determination on each subject according to the FDA monograph proposal.

To ensure standardized information and to establish a product sun protection factor (SPF) value, the application of product is expressed on a weight basis per unit area defining a standard film. The test sunscreen product and the standard sunscreen application are 2 mg/cm² and 2 µl/cm² respectively. The 50 cm² test site area requires 100 mg of product or 100 µl (assuming a specific gravity of 1) to ensure a standard 2 mg/cm² test application. For the test product, a cream, the viscosity is such that the material was weighed and applied to the appropriate area by spreading with a finger cot.

Before exposing the test site areas to light after application of a product, a waiting time of at least 15 minutes was observed.

Using the sun simulator, the sub-areas of each person were irradiated with UV light in series (in terms of duration). A series of irradiations is carried out on the untreated, unprotected skin to determine the MED. The MED is the irradiation duration that causes the least noticeable redness 16 - 24 hours after the irradiation. The MED of the unprotected skin of the test subjects was determined before the test day and again on the test day.

Each of the protected test sites (comparative products and/or sunscreen product to be tested) was also irradiated with UV light. The standard time intervals chosen corresponded to a geometric sequence represented by (1,25)n, where each irradiation time interval is 25% longer than the previous time (the reason for using the geometric UV irradiation sequence is to obtain the same relative uncertainty expressed as a constant percentage, and This was independent of the sensitivity of the respective test person to UV light (regardless of whether the test person had a high or low MED). The exact series of radiations administered was derived from the MED of the unprotected skin.

Subjects #1-5 entered a hot tub for 20 minutes after UV exposure to a test site of the test sunscreen and the control sunscreens mentioned above. The level of agitation in the hot tub was moderate. Subjects #1-5 then rested for 20 minutes and entered the hot tub again for 20 minutes. Care was taken to ensure that each subject was continuously monitored to ensure that the test areas were not touched "after" the test. After the 40-minute immersion, the test areas were air dried without the use of a towel. The second protected test site of the test sunscreen was then exposed to UV light using the same procedure and series of exposures as the "previous" UV light exposure. Each subject again immersed in the hot tub for 20 minutes, then rested for 20 minutes and immersed in the hot tub for a second time for 20 minutes. After completing this 40-minute immersion, the test sites were air dried without the use of a towel. The third protected test site of the sunscreen under test and the second protected test site of the previously mentioned wet control sunscreen were irradiated using an identical procedure and series of exposures as used for the "previous" UV light exposure.

Subjects 6-20 entered the hot tub for 20 minutes after exposing a test site for the test sunscreen and the control sunscreens mentioned above. The amount of exercise in the hot tub was moderate. The subjects then rested for 20 minutes, then another 20 minutes, and finally entered the hot tub for another 20 minutes. Care was taken to ensure that each subject was continuously monitored to ensure that the test site areas were not touched "after" the test. After the 80-minute water test the test sites were air dried without using a towel. The second protected test site of the respective sunscreen product to be tested and the previously mentioned wet control were then irradiated with UV light using the same procedure and using the same irradiation series as used for the "previous" irradiation with UV light.

Each person had to report back 16 - 24 hours after irradiation. At this point, the MED of both the unprotected and protected skin could be determined for each test site area.

For the test sites irradiated before immersion in water and the test sites irradiated after 40 or 80 minutes of immersion in water, the sun protection factor of the sunscreen under test was then calculated from the irradiation time interval required to determine the MED of the protected skin and the irradiation time interval required to determine the MED of the unprotected skin (control site), i.e.

SPF - MED protected skin / MED unprotected skin

calculated.

No adverse reactions were observed in any of the people tested using the test procedures described. The sun protection factor (SPF) values for the sunscreen after 40 minutes of immersion (5 people) and after 80 minutes of immersion (20 people) and for the controls (20 people) are as follows: Product SPF Rating Category Test Material Before immersion After 40 minutes of immersion Controls J&J SUNDOWN Moderate Before immersion Homosalate or greater (Ultra) or greater (Ultra) (Moderate).

Claims (12)

1. A mammalian skin waterproofing agent containing (in % by weight) 1-10% of a C18-C36 saturated synthetic fatty acid wax, 3-30% of anhydrous hydrophobic starch, dispersed in 60-96% of a pharmacologically acceptable anhydrous carrier. 2. Agent according to claim 1, wherein the carrier consists of a mineral or vegetable oil or aliphatic/branched chain ester. 3. A composition according to claim 1, wherein the carrier consists of an anhydrous solvent. 4. Agent according to claim 1, 2 or 3, containing up to 20 wt.% of UV-A and UV-B blockers. 5. A method of protecting (against the harmful effects of solar radiation of a wavelength of 700 - 2600 nm) and waterproofing mammalian skin by applying to mammalian skin an effective amount of a preparation containing (in % by weight) 1 - 10% of a C18-C36 saturated synthetic fatty acid wax and 1 - 30% anhydrous hydrophobic starch, each dispersed in a pharmacologically acceptable anhydrous carrier in admixture with a UV blocker, excluding treatments of the human body as defined in Article 52(4) EPC. 6. A method of protecting mammalian skin according to claim 5, wherein the carrier consists of an anhydrous ointment. 7. A method for protecting mammalian skin according to claim 5, wherein the carrier consists of an anhydrous solvent. 8. A method of protecting mammalian skin according to claim 5, wherein the carrier consists of an anhydrous cream. 9. A method of protecting mammalian skin according to claim 5, wherein the carrier consists of an oil. 10. A method of protecting mammalian skin against the harmful effects of solar radiation of a wavelength of 700 up to 2600 nm by applying to mammalian skin an effective amount of a preparation containing (in 20% by weight) 1-10% of a C18-C36 saturated synthetic fatty acid wax, 1-30% of anhydrous hydrophobic starch, 1-20% of UV-A and UV-B blockers, each dispersed in a pharmacologically acceptable anhydrous carrier, excluding treatments of the human body according to Article 52(4) EPC. 11. A method for protecting mammalian skin according to claim 10, wherein the carrier consists of a solvent. 12. A method for protecting mammalian skin according to claim 10, wherein the carrier consists of a mineral oil.