A demanding regulatory context
While the formulation of sunscreen products was at the heart of In-Cosmetics latest edition, an expert on this subject that we met, was explaining that in his opinion, "the formulation of solar products was first a question of knowing how to take into account the various regulations."
As a matter of fact, given the challenge they represent in terms of public health, the regulatory framework for these products has been considerably reinforced. The content of the European recommendations of 22 September 2006 concerning the protection against UVAs, to which can be added the uncertain status of nanomaterials and the different geographical specificities, make the task of formulators particularly difficult.
Things get even further complicated because of a still partial harmonization of in vitro evaluation methods. "Within the European Committee for Standardization, a group is working on the creation, the updating and the harmonization of analytical methods for cosmetics, including sunscreens. The work of the ISO group on cosmetics comes in support. Concerning solar products, results may differ depending on the used protocols. That is why the creation of harmonized international and European standards will ease the work of formulators upstream. The Commission has already given a positive opinion for an in vitro measuring method of SPFs based on transmittance, at the level of their waterproof efficiency discussions are underway," summarizes Laurence Mulon, Consultant in strategy development and regulatory affairs.
Complying with the UVA/UVB ratio
Another relatively recent constraint this one, is the requirement for each product to be efficient against both ultraviolet B rays (UVBs) and ultraviolet A rays (UVAs). During prolonged exposure, UVBs are the cause for sunburns while UVAs by penetrating deeper cause accelerated aging and may contribute to the development of cancers.
Europe, via Cosmetics Europe, the organization representing manufacturers, the United States but also Asia, thus demands broad spectrum products. In Europe and in the United States, the requirement focuses on a UVA and UVB ratio equal to 1/3 with a critical wavelength of 370nm. A difficult balance to achieve when looking for high SPFs.
It is to overcome this difficulty that Croda launched in 2010 the Solaveil SpeXtra™ range obtained from an exclusive and patented manufacturing process. The TiO2 used enables to have a efficiency on the entire UVA and UVB spectrum. These dispersions help, with no additional chemical filters or ZnO, to obtain high SPFs while respecting the 1/3UVA/UVB ratio. In 2011, the range expanded, with Solaveil XT40W, a dispersion in an aqueous phase thus leaving greater flexibility for the choice of the oily phase and possibly for the addition of chemical filters for very high SPFs.
"With Solaveil XT-40W, formulators can create high SPF natural sunscreens, complying with internationally approved EU recommendations, and with excellent sensory properties," emphasised Julie Saintecatherine, Technical and Marketing Coordinator at Croda. This range obtained the award for the best technology at the Cosmetics & Toiletries R&D Awards.
For its part, the Zschimmer & Schwarz Group offers, under the name HelioPro, a wide variety of titanium dispersions also compliant with regulatory requirements. The HelioPro BSP 50L grade is very appropriate for the formulation of high SPFs with no organic molecules.
As for Kobo, it offers UV Balanced Powder 100, an optimized titanium mixture of different sizes for the 1/3 ratio substantiation.
Minerals screens with studied sizes
In addition to broad protection requirements, the particle sizes offered by suppliers are broadening as a result of the uncertainty on the regulatory future of nanomaterials. Starting 1 January 2013, the European Regulation [1] will make it an obligation to mention on the list of ingredients those whose size is nanometric with the [nano] indication. The Commission’s Recommendation of 18 October 2011 clarifies the definition of nanomaterials as "a nanomaterial is a natural material which contains particles in an aggregate or agglomerate state, and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm - 100nm" [2]
It is in this context that Kobo offers its Non-nano titanium and zinc range, whose name is unambiguous, with particle sizes higher than 100 nm available as powders or dispersions. At the In Cosmetics 2012 show, Kobo also showcased the ACT-50 composite, an innovative matrix of acrylates containing small size particles of titanium or zinc with a good efficiency, with no bleaching effect and preventing the re-agglomeration of particles and with a soft touch.
An broadened action
But sun protection does not stop at UVAs or UVBs and some materials go even further. This is the case with Dermoprotectyl from Rovi, which offers a dual protection thanks to a multiple encapsulation system. This product consists of a mixture of chemical filters combined to a cocktail of vitamins C and E. The technology used enables to maintain filters at the surface of the skin while vitamins penetrate deep in the epidermis thus providing a second line of defence.
Tayca, which is distributed in France by Unipex, positions itself with the MP100 a protection against infrared radiation (IR), these radiations that constitute most (55%) of solar radiation. It is interesting to note that Lancaster has incorporated into its new Sun Beauty line, a protection against IRs.
Suppliers of active ingredients have also added to the array of possibilities newly developed molecules capable of fighting or repairing induced photoaging. Cosmetochem for example presented in Barcelona, Sereniks a natural extract of Tsuga Canadensis with anti inflammatory, antioxidant, properties and of protection against photoaging.
Exsymol with OTZ10 offers a protection against UV and IR induced cell and skin damage. Its optimized bioavailability preserves the quality of skin layers. IRB with Buddleja Davidii Stems G, available in a titrated version in verbascoside is recommended to protect skin against UVAs with its antioxidant, anti-inflammatory and photoprotective properties.
DSM broadens the concept of sun protection by working on the effects of exposure to sub-erythemal doses, i.e., UV doses lower than those leading to sunburn. "At lower UV radiation doses, we are already able to highlight significant damage at the DNA, Langerhans cells level involved in the immune system, in collagen and elastin," emphasised Caroline Ploton, Regional Technical Marketing Manager. DSM recommends the use of Parsol SLX, a polymeric liquid filter that acts synergistically with Parsol HS, a water-soluble filter to reach high SPFs with a light and non greasy texture. PArsol 1789, a universal standard and the most efficient UVA filter, will be added as a complement to UVB filters.
Photostability: a difficult quest
Another important challenge for formulators, although few brands communicate on this subject: products photostability. This ability of the product to keep its efficiency after sustaining a dose of light irradiation, is however very important. A photostable filter re-emits the absorbed energy without being degraded while a photounstable filter under a luminous radiation will fragment into free radicals, change conformation or join other molecules present in the formulation and lose in the process, its UV absorption potential.
Several solutions can help such phenomena from occurring. HallStar, distributed in France by Arnaud-Azelis, is very active in this field. The American company proposes Solastay S1, a molecule of ethylhexyl methoxycrylene, known as an excited singlet-state quencher, that is to say, it can recover the energy absorbed by the chromophores of the UV filter before the latter destabilizes leading it to an excited triplet state or to a change in its structure into free radicals. This activity focusing on the singlet state level is innovative and enables to photostabilize sensitive filters like avobenzone, octyl methocycinnamate (OMC). The photostability potential is greatly increased: 3% of Solastay S1 enables a photostabilization of avobenzone in UVAs of 90% and of 98% in UVBs. For the avobenzone/OMC mixture, the photostabilization potential is of 80% in UVAs and of 84% in UVBs. This year, HallStar marketed Polycrylène S1 which adds water resistance capabilities to photostabilization.
The obligation to provide information in connection with the photostability of sunscreens has not yet become a topical issue, but who knows what the future holds! Meanwhile, to help the general public be aware of the techniques and of the importance of sun protection, Croda has made available to consumers an educational website: www.solaveil.com. The website provides simple and clear information on the science of solar products. It has just been translated into French this year. No more excuses then for not understanding what are SPFs, UVAs, UVBs and other technical terms...
