Creating efficient hair protection: COSSMA

How can an efficient hair care product with protective properties be created when the parameters regulating protection are not as clear as they are with respect to the photoprotective properties of skin? And what are the main characteristics that a hair care product should possess in order to really protect the hair against the most common environmental stressors?

The difference between hair and skin protection

Protecting hair from oxidative damage seems to be a natural consequence of a decade of progress in UV protection and anti-pollution. The concept of skin protection, meaning the avoidance of harmful environmental factors, has been common knowledge for decades. In contrast to skin damage, the effect of hair stress is relatively easy to determine and quantify. Protein damage, loss in hydrophobicity, structural damage, colour fading, split ends, and hair breakage are only some of the visible effects that occur with hair after exposure to oxidative stress. In addition, exposure to sunlight leads to hair discolouration due to melanin oxidation via free radicals1,2. Melanin is a ubiquitous biological polymer containing intrinsic, semiquinone-like radicals. There are two types of melanin, the brown–black pigments (eumelanins) and the less prevalent red pigments (pheomelanins). Melanin granules selectively absorb UV radiation and offer photoprotection but become degraded or bleached in the process.

Even if the consequences of hair damage are of a cosmetic nature only, as hair is not biologically active, they severely impact a person’s well-being from a psychological point of view. The strategies available for skin protection, such as cosmetic and topical treatments, are based on scientific evidence and can be roughly divided into preventive and healing mechanisms. In the case of sun protection for the skin, for instance, there are UV filters that will block harmful electromagnetic radiation and antioxidants or actives that are able to repair and heal the damage as a second line of defence. In the case of hair protection, the same strategies – prevention and healing – can be adopted, even though modifications are necessary, as different biochemical environments and different needs in terms of acceptance of formulations have to be taken into account.

Nonetheless, the state of the art of modern hair protection products does not seem to reflect the knowledge and technology available. To this end, knowing what tools are available to create efficient and high-performing hair protection products is paramount.

"Hair-protective formulas should not contain ingredients that facilitate or accelerate photocatalytic reactions”
Dr Katinka Jung, Managing Director, Gematria

fig. 1 Experimental setup for melanin/free  radical measurement in whole human hair

3. Defining the appropriate strategies to avoid the damage.

The “prevention and healing” strategy used for skin-care products can and should be adopted for hair care as well. As Paracelsus famously suggested, prevention is better than healing. Therefore, the first line of defence is to be built by actives able to prevent UV radiation from penetrating into the hair. This goal can be achieved with the help of UV filters. In contrast to skin care, penetration depth is not crucial for hair care; the hair should be very significantly protected from high-energy UV B wavelengths. Complete protection with organic UV filters is nearly impossible because of the very big surface area to be covered. Film formers and galenic formulas that can spread on the entire hair surface are of crucial importance for the success of the strategy. Also, the photostability of the UV filters used and their combinations will have an enormous impact on the product’s efficacy. The formulas should not contain any active or ingredient that facilitates or accelerates photocatalytic reactions. Examples of photocatalysers, that generate free radicals on exposure to UV radiation include unsaturated oils and, in some cases, fragrances. The formulation should include antioxidants as a second line of defence as well.

After these theoretical considerations, a case report shows how an efficient and high-performing hair spray is created. The starting point is a prototype of a leave-on hair spray. A market analysis identified benchmark hair sprays which claim to protect hair against UV, environmental and oxidative stress. All analysed products are based on actives in water/alcohol as organic UV filters, antioxidants, and film formers.

Case report: Development of a hair care product

The prototype as well as selected market products were analysed regarding their efficacy in protecting the hair’s melanin. To this purpose, human Caucasian brown hair was exposed to UV radiation, and the content in melanin free radicals before and after UV exposure was determined by Electron Spin Resonance Spectroscopy (ESR)3,4. A schematic representation depicts the experimental set-up for the measurements, see fig.1.

The unprotected (placebo-treated) hair showed a huge increase in melanin-free radicals after short UV-exposures. After 15 minutes of UV radiation additional free radicals increased by approximately 60%. This is how the protective effect (hair protection: HP) of the products was calculated:

HP = 1 – [melanin (treated hair)/melanin (untreated)] * 100 and expressed in percentage. The results are shown in table 1.

All the products showed moderate protective effects on the generation of melanin free radicals. The analysis of the protection after different UV radiation times clearly showed that protection decreased with increasing UV doses. Therefore, one reason for the insufficient protection was a lack in photostability of the UV absorbers and the antioxidative actives used. Moreover, natural oils and extracts limited the photostability of the entire formulation and reduced the photoprotective effects. With these modifications to the prototype formula, the required high protection was met:

1. Avoiding adverse photocatalytic reactions due to natural oils, fragrances or extracts in the product under development by analysing all components individually and in combination with respect to their capacity to induce free radical peroxide reactions under UV radiation.

2. Metal ion chelators were added to help prevent hydroxyl radical formation on the hair’s surface and stabilise the formulation. The resulting Prototype 2 showed a higher photostability even after long UV irradiation doses.

fig. 2: Aim: Highly effective photoprotection for hair Analytical parameter: ESR based melanin analysis RHF

Stabilisers and photostable lipids guaranteed the absence of pro-oxidative reactions.

The sensitive components were carefully analysed individually and in combination to ensure the absence of any adverse radical chain reaction under UV radiation. However, the hair protection factor (HP) obtained was considered to be not high enough. Therefore, Prototype 3* was modified and optimised along the following parameters:

1. Photoprotection was increased by using photostable and highly efficient organic UV-filters.

2. The antioxidant system was carefully chosen to provide an efficient second line of defence.

3. Fragrances were analysed and chosen according to their compatibility with the formula and the absence of peroxide chain reactions with adverse pro-oxidative effects.

The optimised product was analysed again by using the same ESR-based analysis on melanin. The protective effect was significantly higher and was stable at high UV-irradiation doses. The optimisation steps led to an increase in the HP value from 18% to 76%, see tab. 2.

How to obtain a hair protection factor of 76%

Highly efficient hair care products should protect the hair from oxidative damage due to excessive UV exposure. Especially the hair’s melanin is sensitive to UV radiation and should be protected. Analysing the melanin free radicals before and after UV radiation is therefore a useful parameter to quantify the protective effect of a cosmetic hair care product. The characterisation by the Radical Hair Protection (RHF) factor facilitates evaluation and optimisation in the course of product development with respect to stability and efficacy and helps to substantiate marketing-relevant and innovative claims, see fig. 2.

Appropriate optimisation strategies led to an increase of hair protection from 18% of the first prototype to 76% of the final hair care product.

*The INCI of Prototype 3 and the references can be found on the Internet – see download panel

Authors: Dr Katinka Jung* (a), Managing Director
Tiziana Ciardiello (b), Senior Research Technologist,
Anna Benedusi (b), Head of Product Development,
Antonio Mascolo (b), R&D Laboratory Technician
Marietta Seifert (a) Head of Laboratory
Dr Thomas Herrling (a), Managing Director
(a): Gematria Test Lab Berlin, Germany
(b): Giuliani, Milan, Italy

www.gematria-test-lab.com
www.giulianipharma.com
*corresponding author

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