Sun protection products are under more regulatory scrutiny than any other cosmetics. Where there aren’t regulations, there are recommendations.
A Recommendation regarding sun protection products was published in the Official Journal of the European Communities on the 26 September 2006. The Recommendation states that products should provide both UVB & UVA protection with the UVA protection being at least equal to one third of the UVB. Sun protection claims are simplified into low (SPF 6, 10), medium (SPF 15, 20, 25), high (SPF 30, 50) and very high (SPF 50+). The Recommendation also states that no claims should be made that products offer 100% protection from UV radiation or that there is no need to reapply. Products should carry a warning about staying in the sun as well as instructions to apply the sunscreen before exposure and to reapply frequently to maintain protection, especially after perspiring, swimming or towelling. Although such Recommendations do not have the force of law, compliance is expected from the manufacturers and suppliers of sun protection products.
The method of determining the ratio of UVA to UVB is the Persistent Pigment Darkening or PPD method and it has to take photostability into account. The ratio is approximately equal to gaining three stars on the Boots system that is in almost universal use within the UK. Mike Brown, Boots’ sun care scientific advisor, gave a detailed paper at the Sun Protection Conference in London last year, comparing the Boots star rating system to the requirements of the Recommendation. He showed that the star rating actually gave a broader spectrum of protection but it did not take photostability into account. When Brown and his team studied the effects of photostability it appeared to be affected as much by higher temperatures as by UV radiation and temperature also affected UVB determinations. Such discrepancies will affect results regardless of the method of determination.
Sun protection products are subjected to more legislative interference worldwide than the majority of cosmetic products. There is disagreement over which UV absorbers can be permitted and about the maximum levels that may be used of those that are permitted. Despite years of discussion and investigation there is still disagreement over the methods for SPF, water-resistance and UVA testing. A recent paper by David Steinberg reviews the different SPF test methods along with the formulae of reference standards, currently approved UVA methods and water-resistance testing. It covers the recent changes in US regulations and lists the approved UV filters permitted in the US, EU, Japan, Canada and Australia and gives their maximum use level and correct ingredient designation and includes a master cross-reference list by INCI designation.
USAGE & ABUSAGE
For at least two decades the formulation and marketing of sun protection products has been SPF orientated, with a race to print ever higher SPF values on the labels. When examining sunscreen efficacy it appears that 12% relates to the product’s characteristics and 88% relates to how the user applies it. The quantity of application accounts for 71% of user influence and uniformity of application for the balance.
If users applied sun lotion at the same level as the Colipa SPF test method of 2mg/cm2 it would amount to 35ml - 40ml per whole body application, which is cosmetically unrealistic, aesthetically unacceptable and, at least for large families, economically impractical. An SPF 25 sunscreen applied half as thick as the amount applied for the SPF test may only have the effect of SPF 8 and an SPF 15 lotion applied in the real world may be more effective than SPF 30. Many investigators agree that the amount applied by most users is between 25% and 75% of the test level and that for the majority the protection received is about half that suggested by the declared SPF.
Several speakers at the Sun Protection Conference questioned the need for everyday sun protection; Brian Diffey was concerned that vital levels of vitamin D were not being generated in some users and Hans Wulf said that there were only about 14 days in the year when the inhabitants of Denmark have need of protection. According to Wulf the yearly dose of UV radiation experienced by Danes is reduced to 75% by use of SPF 2 on all risk days, reduced to 50% by staying out of the midday sun and by 75% by avoiding Mediterranean holidays.
FORMULATION OPTIMISATION
Although sun protection remains a hot topic, in the absence of new permitted UV absorbers formulation emphasis has been on ways of better utilising current actives and material supplier releases concentrate more on minimising the damage that solar radiation causes to human skin cells.
Formulating to the new regulations requires an intelligent approach and qualitative comparisons of absorbance profiles allows UVA/UVB balance to be optimised and the use of broad spectrum filters provides a base upon which to build. The product composition and the combination of actives can have a profound effect on the efficacy of sunscreens. There is synergy between TiO2 and some organics and dissolving the organic sunscreen in the oil phase and using a water-based dispersion of TiO2 in the aqueous phase can be very rewarding, particularly when using combinations of TiO2 with octocrylene or butyl methoxydibenzoyl-methane. Table 1 provides a table of approximate sunscreen efficacy.
The problem of instability with certain combinations of sunscreens is very real. Papers on the author’s website discuss the problem and suggest various answers. Further introductions since their publication include Eusolex UV-Pearls from Merck, which consist of EHMC entrapped in silica that prevents its chemical interaction with BMDBM, leading to an overall significantly improved photostability of EHMC with BMDBM. Octocrylene may also be used to stabilise BMDBM but if EHMC is introduced into the formulation this enhanced stability is largely lost. However, if TiO2 is used instead of EHMC photostable formulations with high SPF and UVA protection are possible. Also from Merck, RonaCare AP [INCI: Hydroxy dimethoxybenzyl malonate] is a colourless oil with strong antioxidant activity that may be used to stabilise BMDBM against photodegradation.
Information from BASF promotes combinations of TiO2 with diethylamino hydroxybenzoyl hexyl benzoate (DHHB) and ethylhexyl triazone (EHT). A mix of 6% TiO2, 5% DHHB and 2% EHT gave SPF 33, with ample UVA protection to meet the EU Recommendation. DHHB is trade named Uvinul A Plus by BASF. It is a new photostable organic UVA absorber with good solubility in cosmetic oils and is compatible with other ingredients such as microfine TiO2 and ZnO.
Surprisingly good results were reported by Michael Schuricht, Symrise at SCS Formulate 2007, Telford, when phenylben-zimidazole sulfonic acid is neutralised with the amino acid arginine. It enabled neutralisation at pH 6.0 without risk of crystallisation and in-vitro protection against damage to Mitochondrial DNA indicates that it may be a useful product to prevent or slow down photoageing of the skin.
Croda now markets the Solaveil Clarus range of TiO2 and ZnO dispersions and it also offers Optisol – TiO2 doped with manganese to prevent free radical formation and to provide broad spectrum protection. This material is available in powder form and as a 50% dispersion in a blend of fatty acid esters. Optisol producer Oxonica has also just introduced a finished product in the form of Optisol Sun Defence, selling online and through spas looking for differentiation. The company says this is just the beginning and plans to launch two or three products a year.
Parsol TX is a microfine TiO2 from DSM. The rutile TiO2 crystals are first coated with silica and then surface treated with dimethicone. This coating is said to be complete and the material has almost no catalytic activity. This ensures photostability of the TiO2, which remains chemically inert and compatible with other ingredients in the final sun protection composition. Experimental results published by DSM show that ascorbyl palmitate remains stable in the presence of Parsol TX and that BMDBM does not crystallise or degrade when incorporated in the same formulation as Parsol TX.
Water-resistance is a required property of sunscreens and complete solubilising of organic sunscreens is necessary for successful formulation. Lexfilm Sun from Inolex [INCI: Polyester-7, neopentyl glycol diheptanoate] is said to combine superior solubilising power for oil-soluble actives with water-proofing properties. Data published by Inolex shows 97% retention of SPF when a formulation containing 5% Lexfilm Sun was subjected to the FDA water-resistance test.
Giovarez AC 5099M and Giovarez BTB 50 are two acrylates copolymers in isodecane from Phoenix Chemical that impart good water-resistance to sun protection lotions and creams. Also recommended for improved water-resistance is Pecogel S1120 [INCI: VP/Dimethiconylacrylate polycarbamyl polyglycol ester]. Pecosil SH-25L [INCI: Dimethicone/methicone copolymer] is of interest for sunscreens containing ZnO as it covalently binds to the surface of untreated pigments giving them a silicone coating and making them water-resistant and substantive.
DAMAGE MITIGATION
Solar radiation is blamed for all skin problems from premature wrinkling to malignant melanomas. It is therefore little surprise that the cosmetics industry is looking for ways of mitigating such damage and investigating natural materials for UV absorption potential and antioxidant activity is the subject of much research.
A study conducted in Turkey on extracts of black tea obtained from the Black Sea region of Turkey determined their UV absorption profile. A peak was obtained between 250 and 300nm. Black tea aqueous extract was incorporated in a carbomer gel and tested in-vivo for its protection potential against UV (200-400nm). It was found that erythema appeared after four hours and reached a peak at 24 hours on the control site, but no erythema was observed in any of the six subjects on sites where the black tea gel was applied. It was concluded that black tea gel protected the skin from a broad range of UV (200-400nm) radiation.
It appears that all teas are of interest when mitigating solar damage to skin. Tealine from Greentech [INCI: Camellia sinensis leaf extract, Aspalathus linearis leaf extract, maltodextrin] is a combination of red, white and green tea with potent anti free-radical properties. Also from Greentech, Protectol [INCI: Dipropylene glycol, Betula alba bark extract, Scrophularia nodosa extract] is said to reduce skin reactivity in relation to various aggressions and to regulate and inhibit inflammatory process.
Environmental insults such as UV rays from sun, cigarette smoke exposure and pollutants, and the natural process of ageing contribute to the generation of free radicals and ROS that stimulate the inflammatory process in the skin. UV irradiation initiates and activates a complex cascade of biochemical reactions that cause depletion of cellular antioxidants and antioxidant enzymes initiate DNA damage and release of pro-inflammatory mediators from a variety of skin cells. The inflammation and ROS also cause oxidative damage to cellular proteins, lipids and carbohydrates, which accumulates in the dermal and epidermal compartments, contributing to the aetiology of photoageing.
Strategies to prevent photo damage caused by this cascade of reactions initiated by UV include: prevention of UV penetration into skin by physical and chemical sunscreens; reduction of inflammation using anti-inflammatory compounds; scavenging and quenching of ROS by antioxidants; inhibition of elastase activity to prevent extra-cellular matrix damage and activation of matrix metalloproteases (MMPs); and inhibition of MMP expression and activity.
Tocopheryl phosphate has recently been identified as a naturally occurring a-tocopherol derivative and has been detected in several human tissues and plants. In this form, it is said to have bio-functional activity as a modulator of cellular inflammation pathways as well as antioxidant properties. When tocopheryl phosphate is effectively delivered to the outer epidermis through topical formulations it reduces many of the symptoms associated with sensitive skin such as redness, irritation, swelling and itching. Vita ET from ISP [INCI: Disodium lauriminodipropionate tocopheryl phosphates] is an improved form of tocopheryl phosphate optimised for transdermal delivery.
Pepha-Protect from Pentapharm [INCI: Citrullus lanatus extract] is a skin protective active containing naturally occurring vitamins, carbohydrates and amino acids such as citrulline extracted from watermelon. Under extreme conditions watermelon plants develop their own defence system by producing compatible solutes. These are water soluble molecules, eg amino acids, which penetrate easily into the skin and they occur naturally in the human body. Pepha-Protect is offered as a preventative ingredient to protect skin against breakdown of DNA caused by UV light and pollution.
Actimp193, Expanscience Laboratoires [INCI: Hydrolyzed lupine protein] contains low molecular weight purified white lupin peptides obtained from lipid-free seeds that is said to decrease MMPs production in irradiated human fibroblasts. Also from Expanscience, a-Lupine [INCI: Lupin oil, wheat germ oil unsaponifiables] is suggested as an elastase inhibitor and for preventing peroxidation of lipids. The third material from Expanscience comprises cosmetically active molecules from wheat germ and sesame oils extracted by molecular distillation and combined to form Hierogaline, a free radical scavenger for pre and post sunning products.
Cosmo 100 from Evonik [INCI: Creatin] is an amino acid derivative said to repair sun damaged DNA through the activation of the thymidine dimer removal process and to significantly reduce the number of sunburned skin cells. Defensil from Rahn is a three-part mix of Cardiospermum halicacabum extract that is effective against itching and allergic skin rashes plus echium oil that possesses anti-inflammatory properties through its stearidonic acid content and the unsaponifiable elements of sunflower oil that provide valuable nutritional elements such as phytosterols, tocopherols and squalene.
Winner of the BSB Innovation Award,
in-cosmetics Paris 2007, Symrepair from Symrise is a mixture of hexyldecanol, bisabolol, stearic acid, cetylhydroxyproline palmitamide and Brassica campestris (rapeseed) sterols. It is an effective synergistic blend of the three key components of the barrier lipid combined with the anti-irritant action of bisabolol. Studies show it protects and repairs the skin barrier and reconstitutes lamellar bilayers when these become damaged through environmental factors.
DN-AGE LS 9653 [INCI: Aqua, glycerin, Cassia alata leaf extract] is supplied by Laboratoires Sérobiologiques as an active ingredient for preventing UV induced DNA damage on both nuclear and mitochondrial DNA. Carotenoids are interesting materials of natural origin with antioxidant properties but are usually highly coloured, which limits their use in cosmetics. Symrise has produced colourless carotenoids from tomato and from algae. They are said to have outstanding protective capabilities and to boost and stabilise other actives such as b-carotene and CoQ10.
GluCare N and Glucare S are b-glucan and sodium carboxymethyl b-glucan respectively from Evonik. Both materials are obtained from the cell wall of the yeast Saccharomyces cerevisiae. GluCare N is oil-soluble and GluCare S is water-soluble. Experiments show that just 0.1% GluCare S in a topical preparation is effective in protecting Langerhans cells against the damaging effects of UV radiation, thus supporting the natural immune system.
Reducing inflammation and inflammatory responses is a crucial part of mitigating sun-induced damage. RonaCare Ectoin acts as an anti-inflammatory active by regulating proinflammatory signals in human keratinocytes. Ectoin also promotes the expression of heat shock proteins in human skin cells. Heat shock, or stress proteins are a universal cellular protection mechanism in all organisms that stabilise, repair and support the removal of damaged proteins. By accelerating their production in cells under stress Ectoin provides accelerated protection to the skin cells against external stress factors.
Also aimed at producing heat shock proteins is Preparami from Alban Muller [INCI: Simmondsia chinensis (jojoba) seed oil, Opuntia ficus indica fruit extract]. This latter material is better known as prickly pear and is found on desert dwelling cacti, which have to survive extreme conditions of heat, cold, drought and strong sunlight. Thymophytane is an active ingredient for anti-ageing and sensitive skin care products from ISP-Vincience obtained by selective extraction of the protein fraction of rice (Oryza sativa) grains. It provides skin with rice peptides similar to thymic peptides that normalise skin immune defence, protect skin structure and integrity and reinforce skin barrier function.
Peptides are currently in vogue as active cosmetic ingredients. Exsymol offers a pseudopeptide trade named Imudilin [INCI: Glutamylamidoethyl imidazole]. Although free radicals are generally considered toxic species for biological organisms it has been shown that some of them take part in essential physiological processes. Some free radical species are also communication messengers produced by numerous cells, in particular in the skin. As an example, fibroblasts and lymphocytes continuously produce small quantities of superoxide anion that regulate cell growth. A common characteristic in the process of transduction is that the quantities of free radicals involved are always very low. Very low levels of Imudilin release sub-toxic quantities of superoxide anion in skin cells that actually improve immune cell response by stimulating their signal transduction pathway.
Not all ingredients are from natural sources. Batyl alcohol, obtainable from Nikko Chemicals Co, inhibits the release of inflammatory cytokines, interleukin and prostaglandin produced by UVB-irradiated keratinocytes. In skin care formulation batyl alcohol performs three functions: it improves texture, increases stability and provides anti-inflammatory, anti-stress and DNA protecting effects. Also from Nikko is Nexbase [INCI: Hydrogenated polydecane]. It has good dispersion properties for mineral-based sunscreens and is an excellent solvent for oil-soluble organic ones.
MELANIN BOOSTERS
One method of providing UV protection is to boost the body’s natural production of melanin. Melactiva from Lucas Meyer [INCI: Mucuna pruriens seed extract, maltodextrin] is a natural tan accelerator with L-DOPA extracted from an Asian fruit, kapi kacchu, also known as velvet beans. It stimulates UV-induced melanin production and promotes a natural tan under reduced UV exposure. Tyrosilane from Exsymol [INCI: Methylsilanol acetyltyrosine] also activates the production of melanin and the silanol has some antioxidant activity. Oligodyne-1 Complex from Vevy Europe is a mixture of metal aspartates designed to help renew damaged skin and promote a tan.
Active Concepts suggests AC Tan Accelerators [INCI: Aqua, phospholipids, tyrosine, Saccharomyces zinc ferment] for accelerating sun tanning, and Alban Muller provides Actibronze [INCI: Hydrolyzed vegetable protein, tyrosine] for the same reason. Solar radiation causes a melanocyte stimulating hormone to be released and melanin to be produced. AC Dermapeptide Tanning from Active Concepts mimics the hormone signal and activates melanocytes without the stimulus of sunlight.
Tosilin from the Gova Group is a complex containing low molecular glucomman and water soluble beta-glucan with bioactive sodium hyaluronate in aqueous solution. It is extracted from yeast and microscopic mushrooms in controlled conditions. Tosilin optimises melanocyte activity thus accelerating the tanning mechanism and an increase in natural sun protection. From Lucas Meyer comes Melactivas [INCI: Mucuna pruriens seed extract, maltodextrin], described as a natural tan accelerator that is extracted from kapi kacchu seeds. Its high L-DOPA content (30%) stimulates UV-induced melanin production and provides a natural tan to the skin.
FAKING THE EFFECTS
Spray tanning and other chemical induced tanning processes have largely replaced the sun bed in tanning studios. At one time these were hit-and-miss and few thought hideous orange a satisfactory substitute for a tan from the Costa Brava. But technology has moved on and results are now very acceptable.
Dihydroxyacetone (DHA) remains the prime ingredient of chemical tanning products. The mechanism is a reaction of DHA with the amines, peptides and free amino acids in the stratum corneum in a Maillard reaction, resulting in yellow and brown coloured reaction products with the various amino acids involved. It appears that there is an initial reaction with soluble amines in the stratum corneum followed by incorporation into skin. Human skin contains just enough soluble amino compounds to trigger a vigorous reaction with DHA, without blocking incorporation of intermediates into skin surface proteins.
Nanospheres 100 from Exsymol are very small sized particles with high adsorption abilities that are loaded with DHA for slow release to the skin, resulting in a more homogenous tan. Sustained release is also obtained from DHA 50% Cyclosystem Complex from Istituto Ricerche Applicate (IRA). It is a 50% mix of DHA with cyclodextrin. DHA activity is enhanced by the cyclodextrin and the controlled release guarantees a constant and prolonged presence of DHA on the skin and prevents irritating reactions occurring with the free form.
DHA Rapid from Merck generates a smooth and particularly even skin tone within a very short period of time and has anti-inflammatory and anti-ageing properties. A combination of DHA and troxerutin, the latter is an effective anti-inflammatory agent used in cosmetics for its antioxidant effects. For users looking for natural credibility, Soliance produces Ecocert approved DHA by fermentation of renewable plant substrates. Alban Muller has introduced Instabronze [INCI: N-acetyl tyrosine, dihydroxyacetone], which improves the tanning mechanism by ensuring sufficient amine is present in the skin but it is prevented from premature reaction by encapsulation.
Erythrulose is also used in sunless tanning products, usually in combination with DHA. It produces a lighter and slower developing tan than DHA and only reacts on the skin’s surface and does not seem to penetrate beyond the dead surface skin layers. When used alone, it fades faster than DHA and some people feel the final tone of erythrulose is slightly redder and less bronze than a DHA-based tan. It may be less drying to the skin surface, helping provide a smoother fading tint. When combined with DHA, the resulting sunless tan is said to last longer, fade better and provide a more cosmetically pleasing colour tone.
Emerging trends in personal care are oral supplements for skin care and protection against UV damage. LycoRed of Australia has been granted a patent for a carotenoid composition of lycopene, phytoene, phytofluene and vitamin E that protects the skin from the damaging effects of UV radiation when taken orally. A recently granted US patent is for a photo-protection composition comprising an extract of polypodium leucotomos plus the carotenoids astaxanthin and lycopene and includes superoxide dismutase and N-acetyl cysteine for oral administration.
References at www.cosmeticsbusiness.com
