In vivo measurement of oxidative stress in human skin
Modern cosmetics with anti-ageing efficacy claims are complex mixtures containing UV-filters and antioxidants and rely on substantiated scientific methods for efficacy testing.
Generating free radicals and thereby oxidative stress, sun light (UV-radiation) is the main cause for premature skin ageing (photo ageing).
The biggest challenge in terms of claim support is a non-invasive but sensitive in vivo measurement of oxidative stress of human subjects. Only such an in vivo approach takes into account all physiological processes active in living skin providing efficacy data with greatest relevance to the in-use-situation.
UV-filters and antioxidants decrease radical generation and pro-oxidative processes so they ensure a quicker and/or more effective radical protection and detoxification.
Measuring chemiluminescence (ultra-weak photon emission) accompanying radical reactions in biological tissues such as skin, the ICL-S method (induced chemiluminescence of human skin) permits the non invasive measurement of oxidative stress in real time in panels of human volunteers.
Efficacy testing of antioxidants and UV-filters can be performed for raw materials, during products development and for finished products after topical application (in-use situation).
Blue light and High Energy Visible Light (HEVL) protection can be investigated by this technique as well.
Predefined benchmark formulations raise the bar for future product development and selection of active ingredients.
In summary, chemiluminescence-detection (ICL-S) is currently the state-of-the-art technique for a non-invasive in vivo measurement of oxidative stress in human skin providing highest relevance of the obtained data.
In vitro measurement of UV and heat protection of human hair
Beside the positive aspects of sunlight it should be taken into consideration that hair is adversely affected by sunlight.
UV light penetrates into the inner part of hair, bleaches hair pigments, and attacks hair structure.
It is well known as well that a high temperature of heat irons damages hair. Hair care products may either countervail or reduce these damages.
Chemiluminescence is the emission of light, as the result of a chemical reaction. Although hair is not living anymore, redox reactions take place in hair, which also lead to permanent emission of photons out of the hair, which is measurable.
All kind of damages in hair are accompanied by a change of this redox system. If hair is damaged (e.g. light, heat, chemical treatment) the redox system is changed and a change of photon emission is measured.
This characteristic is used for the ICL-H method (induced chemiluminescence of human hair in vitro) to determine different hair protection claims:
E.g. in order to show the UV protection of products, hair is irradiated for 3†s by UV light and the emitting photons are detected before and after product treatment.
Applied UV filters reduce the penetration of light into hair and reduce the change of the redox system. Thus, the chemiluminescence method shows a direct proof of protection.
Furthermore, no pre-damage of hair or no long exposure to UV light is necessary to detect UV protection, which makes the chemiluminescence method to a fast measurement tool.
The ICL-H technique is a very sensitive method to detect UV and heat protection of hair care and hair styling products.
All tests include statistical analysis. Thatís understood.
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