Sun Care beyond Filter

Interview with Stanisław Kruś
Senior Technology Manger Sun Care and Senior Lab Leader at Global Technical Center Sun Care at BASF Grenzach GmbH

You are part of the BASF’s team at the Global Technical Center for sun care. What are your responsibilities?

I’m leading the technical service laboratories at the Global Technical Center of BASF. 

We’re providing technical support to sun care producers, sharing our experience and know-how on formulating and performance aspects of sunscreens.

What are the recent tendencies – where is the sun care market heading?

Developing new sunscreens today, has turned out to be highly challenging due to both the unclear fate of some approved UV filters mainly in Europe and, also other regions, as well as the hurdles to register new UV filter molecules. From the UV filters under scrutiny, the widely used UVB filters Ethylhexyl Methoxycinnamate (EHMC) and Octocrylene (OCR) are being heavily discussed due to rising concerns regarding their safety profile for humans and the environment.

In addition to the issues put forward by official authority bodies, sunscreen manufacturers must also consider the perceptions of the end consumers, who are more concerned than ever of how they personally impact the environment. And they are increasingly adjusting their consumption accordingly. On the other hand, consumers are also more and more aware about the need for UV protection and they expect products with high performance and high-end sensory profiles. 

The uncertainty regarding the legal fate, in addition to the reticence of consumers, explains the willingness of sunscreen manufacturers to pro-actively remove some widely used UV filters such as EHMC and OCR from their new sunscreen developments. This removal results in a real challenge in terms of the performance achievement of sunscreen formulations.

How does BASF manage this challenging situation?

Formulating new sun care products under these circumstances isn’t easy. Not only are there fewer UV filters to choose from that the market will accept, but the right combination of the UV filters must also be selected. This is where we offer our expertise.

What does that mean? 

As mentioned before, OCR and EHMC are less and less used in sunscreens nowadays. UV absorbers such as Ethylhexyl Triazone (EHT) and Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine (BEMT) are promising ones, which could be used in modern sun care products. They are characterized by their high molecular weight, they have very good safety profiles, and they show high photostability. When they are used, however, in combination with the common UVA filter: Butyl Methoxydibenzoylmethane (BMDBM), their photostability decreases. One of the consequences of photoinstability is the generation of free radicals in formulation, what can lead to adverse skin reactions. 

When we combine EHT and BEMT with an alternative UVA filter, Diethylamino Hydroxybenzoyl Hexyl Benzoate (DHHB) we do not observe that phenomenon. DHHB and its combination with EHT and BEMT are fully photostable.

Therefore, the combination of EHT and BEMT with DHHB is a good choice when creating modern sun care formulations, without UV filters under discussion.

Can the formulation of the base / chassis help to achieve improved protection?

Sunscreen performance depends on the UV filters used – their absorbance, their concentration and combination, but also on the type of vehicle used.

Indeed, in terms of SPF, we found that the efficacy of the sunscreens depends on the sunscreen formulation chassis, relating to the film thickness distribution of applied sun care products.

In the SPF enhancement study, we found that a water-in-oil emulsion has the highest SPF and highest film thickness, followed by an oil-in-water cream, an oil-in-water gel cream, an oil-in-water spray, and an alcoholic spray formulation, with all the formulations containing the same filter combination. 

We are looking further into that topic and we are trying to identify ingredients which can have a positive impact on sunscreen performance, such as emulsifiers in oil-in-water emulsions or hydrophobic waxes such as hydrogenated castor oil (Cutina HR Flakes). That group of ingredients may impact the film thickness and its homogeneity, and thus have a positive influence on the SPF value. 

What about “magic ingredients” such as boosters? Are they on the rise and what exactly is it that they are doing?

One essential requirement for high SPF is the presence of a UVA filter in the filter combination.

Enhanced photoprotection can also be achieved by the combination of organic oil-soluble UV filters with water dispersible UV absorbers in the form of microfine particles such as MBBT (Tinosorb M) and /or TBPT (Tinosorb A2B). Those materials not only absorb but also reflect and scatter UV radiation, and therefore lengthen the efficacy of soluble UV filters used together in a formulation. 

It is interesting to observe that in the EU market other ingredients which provide protection (absorption) of UV light have not been registered as UV filters. They are marketed as stabilizers of an instable UV filter (BMDBM). They contain the same UV absorbing chromophores as registered UV filters, but they have not gone through the registration process and were not evaluated for human safety. 

This is a paradox because on one side, the UV filters have been re-evaluated in respect of their safety and the legislation has been adapted (e.g., the maximum concentration of Homosalate reduced to 0.5% for body sun care) and on the other side, there are those materials that are used without the same safety evaluation as required by UV filters. 

The EU Regulation clearly states that in cosmetic products claiming UV protection, this must be provided by the UV filters listed in ANNEX VI of the Cosmetic Regulation 1223/2009. 

Therefore, it is not in line with the Cosmetics Regulation to use ingredients with inherent UV absorbency that are not listed in Annex VI.

The right decision is to select ingredients which have no own absorbance but can enhance the protection of sunscreen when used in combination with UV filters. 

Such an effect can be achieved by using particles which lengthen the UV radiation path in the sunscreen film when applied to the skin. This phenomenon increases the chance that UV radiation will hit the molecule of the UV filters and enhance their efficacy. 

We were pleased to present such a product at this year’s in-cosmetics in Barcelona. The natural-based, functionalized calcium carbonate and hydroxyapatite particle is dimensioned in micrometers.

It is of natural origin, not polymer-based, and does not leave a white cast on the skin. It improves the SPF and UVA-PF values as shown in several formulations using in vivo and in vitro studies.

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