Interview with:
Dr Katinka Jung,
Managing Director Gematria Test Lab
Berlin, Germany
www.gematria-test-lab.com
jung@gematria-test-lab.com
COSSMA: What effects does pollution have on the skin?
Dr Katinka Jung, Managing Director, Gematria Test Lab: Skin damage arising from pollutants such as gases and particulate matter is mainly mediated by oxidative stress. The pollutants directly or indirectly generate free radicals on and in the skin, leading e.g. to MMP upregulation and damage of collagen fibres. The mechanisms seem to be similar to those of UV light. Particulate matter, e.g. from combustion smoke, tends to contain heavy metals, metal ions, and organic toxins, which further promote the generation of free radicals on the skin. In addition, the combination of pollutants and UV irradiation can accelerate the radical chain reactions.
Is pollution and skin protection a topic exclusively for the Asian market?
I don’t believe that the pollution problem is limited to Asia or major cities. The effect of many pollutants, such as metal ions and organic radicals, is not necessarily dose-dependent, but a catalytic. This means that even small amounts of pollutants may start radical chain reactions, behave as photocatalytic agents or induce peroxidation. Especially for sensitive skin or impaired barrier function, this can turn out to be a major problem.
What are the most skin-damaging pollutants?
There are many definitions for what the most aggressive pollutants are. The answer will depend on the biological endpoint determined and the entity of the damage measured. When we define pollutants as the chemical and physical influences that will increase oxidative stress, we have to include ultraviolet radiation, ozone, volatile organic compounds, reactive oxygen and nitrogen species, metal ions and polycyclic aromatic hydrocarbons. Most of these can be found in cigarette smoke, for example.
What ingredients can be used to stop damage caused by pollution?
The approach to efficient anti-pollution strategies is surely to reduce oxidative stress that is induced on the skin’s surface. Preventive strategies that avoid contact of the aggressive particles with the skin are the most efficient. To this end, film formers and formulations that prevent penetration are required. In addition to this, many radical reactions are initiated by UV irradiation. An effective approach to limit this type of damage is to reduce the amount of UV light that reaches the skin. In most cases this can be achieved with the help of UV filters or absorbers. A sunscreen formula is surely helpful. In addition, addressing the metal ion contribution in peroxidation reactions is mandatory for an efficient anti-pollution product. In this context, efficient chelators that trap the metal ions, inhibiting their contribution in radical propagation, are a key factor. The healing strategy of reducing radical damage once the ROS are formed thus is a second line of defence. Efficient and highly reactive antioxidants are needed to stop radical chain reactions and limit lipid peroxidation of the stratum corneum. Actives aimed to restore the barrier function of the skin are helpful to increase the skin’s intrinsic defence system.
What evidence is there that cosmetic ingredients really counteract the damaging effects of pollution?
We observe a constant increase in raw materials claiming efficacy against pollution-induced damage on skin and hair. Again, prevention and healing are the main strategies to fight pollution effects. The mechanisms of action can range from removal of the pollutant particles, for cleansing products, to antioxidant actives aimed to reduce the oxidative stress. An efficient anti-pollution product seems to be a synthesis of different actives in a proper formulation. The matrix formulation is key to help the actives to be efficient. No photocatalytic activity should occur inside the formula, in order to prevent additional chain reactions.
What testing methods help to verify this?
Direct or indirect measurements of oxidative stress on the skin are able to show the effect of pollution on the skin and can prove the efficacy of anti-pollution formulas. The test methods can either be ex vivo or in vivo. There are no regulations or guidelines for efficacy testing yet. Therefore, there is a wide range of different testing methods and experimental set-ups. The anti-pollution claim is applied for different classes of products, from leave-on skin protection to rinse-off cleansing. Accordingly, the test methodologies are as diverse as the products classes. A common standard active would be helpful to be able to compare the data from different measuring endpoints. Comparison studies among in-vitro and in-vivo tests are also helpful to obtain more reliable results. As an example, a strong correlation has been shown for ex-vivo tests measuring the amount of free radicals on skin explants due to cigarette smoke and lipid peroxidation markers on skin biopsies coming from in-vivo clinical studies.
What combination of ingredients contribute to reducing the effects of pollution?
For each anti-pollution strategy the formulation plays a major role. The matrix should prevent the contact between the aggressive environment and the skin barrier. Therefore, a formulation containing penetration enhancers or even a formulation facilitating the skin absorbance is not exactly what is needed here. Furthermore, as many oxidative processes are accelerated by UV radiation, the formulation could contain UV-filters to reduce radical chain reactions from the very beginning. Metal ion chelators might be helpful, but only in the case when the resulting coordination complexes really reduce the catalytic metal activity. This can be achieved with the help of chelators that precipitate or reduce the metal ions, removing them physically or chemically from the reaction system. Antioxidants can be helpful if they are powerful and stabilised. For anti-pollution purposes, the antioxidants don’t even need to penetrate deeply into the skin, as they have to prevent lipid peroxidation of the stratum corneum in the first place. Finally, but not less importantly, there should be a major emphasis on making sure that there is no photocatalytic activity inside the formula. The smartest concept of anti-pollution becomes meaningless if adverse peroxidation occurs in the matrix, due to oil or perfume oxidation or photocatalysis of actives. The combination of actives has to be carefully tested and each component should be optimised to guarantee the highest performance.
Is there any evidence for this?
We are constantly testing formulations with potential anti-pollution effects. The test has been developed based on ESR spectroscopy, with which the effect of a formulation on reduction of radical reactions in the presence of pollutants and UV radiation can be determined. Due to our experience with these tests, we know which ingredients and formulations work well.
What potential is there for anti-pollution skin care?
If the anti-pollution concept is not only considered a marketing claim, but an authentic need to protect our skin from the negative environmental factors, the potential is enormous. This would, however, require a set of standard testing methods, a stricter definition of pollution and deeper insights into the clinical consequences of pollution and the benefits of efficient skin protection products.