Filters used in sunscreen products

Each UV filter works in its own way, but they all have one basic task - to protect the skin from harmful radiation. The choice between a physical, chemical or organic filter affects not only the efficacy of the product, but also its stability, safety and compliance with current legislation. The type of filter used may also determine the need for additional labelling on the cosmetic label. If you are involved in the development of cosmetics with a sun protection function, it is useful to know the currently permitted categories of UV filters, which ones may cause allergic reactions and how their evaluation and documentation is carried out.

UV filters - what makes them different and what do they have in common?

UV filters in cosmetics are designed to protect the skin from the effects of exposure to ultraviolet radiation, which is divided into two main ranges: UVA and UVB. Although both are invisible to the naked eye, their effects differ significantly - both in terms of depth of penetration and consequences for the skin. Therefore, before a sunscreen cosmetic sees the light of day, it should pass the testing of sunscreen products.

UVB - what is it? It is a shorter wavelength radiation (280-315 nm) that has a mainly superficial effect. It is responsible for erythema, sunburn and epidermal damage. Its intensity increases in summer, especially during the midday hours. UVB can lead to DNA mutations and the development of cancerous lesions.

UVA radiation (315-400 nm) penetrates deeper - down to the dermis layer of the skin. It accelerates the ageing process, weakens collagen fibres and can cause hyperpigmentation. Importantly - it works all year round, even on cloudy days, and also penetrates glass.

Therefore, an effective UV filter should provide broad-spectrum protection - against both UVA and UVB. In practice, this means combining different active substances in a single formulation in order to effectively adapt the sun protection to the skin type and the nature of the cosmetic.

UV filter categories - how not to get lost in it?

There are three main UV filter categories:

• Chemical filters - absorb UV radiation, converting it into thermal energy.
  
• Physical filters - reflect or scatter radiation, acting as a microscopic shield on the surface of the skin.
  
• Organic filters - These are often substances created on the basis of organic chemistry, often included in chemical filters, but sometimes treated as a separate category due to their specific properties. They can provide protection against specific UV ranges, often used in combination with other filters to increase the range and effectiveness of protection.
  

Choosing the right filter depends on many factors: the form of the cosmetic (emulsion, spray, stick), its intended use (face, body, children, people with AD), and its compatibility with other ingredients. At the product design stage, it is worth considering not only the effectiveness of the protection, but also possible skin reactions and regulatory requirements. At this point, the question often arises: chemical or mineral filter? The answer is not universal - it all depends on the formula and the target group.

Chemical filters - examples and limitations of use

Chemical filters are the most commonly used group, mainly because of their effectiveness and invisible action on the skin. They act 'inside' the skin in the stratum corneum, absorbing UV radiation and converting it into a safe form, usually thermal energy, which is then dissipated.

Chemical filters - examples:

• Octocrylene
  
• Avobenzone (Butyl Methoxydibenzoylmethane)
  
• Homosalate
  
• Ethylhexyl Methoxycinnamate
  

The use of UV filters in cosmetics is regulated by various acts and guidelines, which define the acceptable ingredients, their concentrations and safety and labelling requirements, e.g. Regulation (EC) No 1223/2009 on cosmetic products - Annex VI of this regulation contains a list of permitted sunscreens with maximum concentrations. Already at the formulation stage, it may be helpful to cosmetic composition assessmentto avoid problems when marketing a cosmetic product.

Physical filters - operation and properties

Physical filters, also known as minerals, work differently to chemicals - instead of absorbing UV radiation, they reflect it and diffuse it onto the skin's surface. They act immediately after application, making them suitable for sensitive skin and children.

Among the most commonly used are:

• Zinc oxide
  
• Titanium dioxide
  

These are not penetrating filterswhich translates into their higher safety profile. The disadvantage may be a skin-whitening effect, which can be minimised by appropriate fragmentation and stabilisation in the formulation. However, before a cosmetic with such a filter is placed on the market, it is worthwhile to carry out a thorough cosmetics research - especially in the context of the claimed level of sun protection.

Natural UV filters - are they a viable alternative?

Natural UV filters are often of interest to natural cosmetics manufacturers, but it is worth separating marketing claims from legal requirements. Raspberry seed oil, shea butter or carrot oil show some antioxidant and protective properties, but cannot replace the UV filters allowed by the regulation if the product is to have an SPF label.

They can, however:

• support the skin barrier,
  
• have a soothing and regenerative effect,
  
• supplement the protection provided by physical and chemical filters.
  

When planning a cosmetic based on such ingredients, it is advisable to consult the market strategy at the outset - preferably even before registration of cosmetics.

UV filters for hair - how do they work and what to look for?

UV filters for hair protect the hair structure from damage, colour loss and breakage caused by UV radiation. They are usually found in leave-in products - conditioners, mists and sprays.

They do not require an SPF declaration, but are subject to evaluation for efficacy, stability and possible allergic reactions. It is worth including this aspect in the technical dossier, and preferably subjecting the formulation to a cosmetics testingbefore the product is placed on the market.

Sun protection - more than just a filter

Sun protection is not just about choosing the right UV filter. It is also about formulation work, tests to confirm SPF claims, stability analysis and compliance of documentation with current legislation. A well-crafted product should be effective, safe, aesthetically pleasing to use - and legally compliant.

Before a cosmetic is placed on the market, it is worth going through a comprehensive assessment of the composition of cosmetics and prepare full EU-compliant documentation. It is a process that pays to plan ahead - not only for user safety, but also for brand reputation.

If you are developing a product with a UV filter and need support with analysis, labelling or documentation - contact our cosmetics laboratory.