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Part 1 - A sun protection guide
The sun's rays can be lovely and many of us love spending time in the sun. In fact, if we enjoy the sun in reasonable amounts, it can provide us with many good health benefits. Being over-exposed to UV radiation, on the other hand, can lead to problems such as painful, red and inflamed skin, but also cause more long-term effects such as premature aging of the skin with deep wrinkles and pigment spots or, in the worst case, various forms of skin cancer. To protect yourself from the sun's harmful rays, you can try to minimize the time you spend outdoors when the sun is at its highest in the sky, wear a protective layer of clothing, a sun hat, and apply sunscreen to exposed skin. And precisely these - the sun protection products - we'll dive into them now!

The harmful UV radiation

When we think of sunbathing, our thoughts often drift towards a wonderful day at the beach, but as you know, the sun's rays are far from just healthy. Sun rays contain different types of radiation that have different wavelengths, among them the harmful UV rays. Ultraviolet (UV) radiation is invisible to the human eye and comes in different varieties - UVA which has the longest wavelengths (320-400 nm) and least energy, UVB (290-320 nm) which is in between and UVC which has the shortest wavelengths (below 290 nm) and highest energy. The earth's ozone layer helps and protects us from all the sun's UVC rays, while the UVB radiation penetrates the outermost skin layer and stimulates the melanocyte to produce more pigment. The UVB rays are also linked to DNA damage and skin cancer such as malignant melanoma. The UVA radiation reaches even deeper into the skin layers and can cause premature aging such as fine lines, wrinkles, dilated blood vessels and spider veins.

Important information:

UVB penetrates the epidermis but not the dermis and does not pass through a glass window.

UVA penetrates deeper into the skin and the radiation penetrates the dermis. It also goes through a glass window.

UV index - tells us how dangerous the sun's rays are

The UV index is an international standard used to measure how intense - and thus harmful - the sun's UV rays are. Using it, we can compare how intense the UV rays are at different places and times of the day. The higher the index value, the stronger the UV radiation you are exposed to. An illustration of the UV index in Figure 1 shows what the UV index normally looks like in Sweden.

In Scandinavian countries the UV index is usually between 4 - 7 during the summer season and between 0-2 during the winter, this could explain our longing for the sun every spring! With a low UV index, you do not need to use sunscreen, but with a high UV index where the radiation is more intense, you must protect yourself, because a high UV index increases the risk of negative effects.

It is important to protect yourself against both UVA and UVB radiation, therefore a good sunscreen should provide protection against both. The sun protection factor (SPF) primarily describes the product's protection against the sun's UVB radiation, where a higher SPF provides better protection. The highest SPF you can see on a sunscreen product is SPF 50+, which means very high protection. Products marked with a UVA symbol (the letters UVA surrounded by a ring) mean that they provide adequate protection against the sun's UVA rays. To get the protection promised on the packaging, you need to apply the product in an even and thick layer. To be able to maintain good protection, you should reapply the sunscreen at regular intervals, especially if you have been swimming or exercising. However, creating a product that provides protection after bathing and exercise is a challenge because it requires the product to be water resistant while not feeling too sticky to wear on the skin.

(Example of what a typical summer day can look like in Scandinavian countries)

How does sunscreen work?

Sunscreens contain active substances called UV filters. These substances protect the skin by absorbing and reflecting harmful UV rays from the sun. In order to achieve effective and balanced protection against UV radiation, a combination of different UV filters must be used. Sunscreens may only contain specified active substances and only in approved quantities. These substances are included in regulations and regulations, and are regulated by authorities such as the Swedish Medicines Agency, the FDA in the USA and the CFDA in China. Developing and manufacturing sun protection products that meet all these requirements, that provide good and broad-spectrum protection and that also feel pleasant to the skin is a complicated and costly process.

The protective UV filters used in sunscreens work by either absorbing or reflecting the sun's UV rays - or a combination of both. In this way, they reduce the amount of harmful UV radiation that penetrates the skin and affects the body's cells. Therefore, the sun protection filters must remain on the surface of the skin to be effective.

When talking about UV filters, they are usually divided into organic filters and mineral filters. The difference between the two forms is mainly that organic filters are soluble in the product, while mineral filters remain as particles. Another difference is also what they are made of, organic filters are organic (based on carbon) molecules while mineral are as the word reveals - mineral based. However, this is not entirely true, some new and modern organic filters are also particles and can therefore be seen as mineral filters. Different UV filters have different properties and differ both in effectiveness and in how they affect the skin, and it is important to make a careful choice when developing sunscreen.

Organic filters

Most UV filters that are approved and used in sunscreens are organic filters in the form of either powders or oils. For the powder filters to be effective, they must be dissolved in oils and fats. The higher the SPF, the more UV filters must be used and correspondingly more and higher levels of oils for the powder to dissolve in the formulation. The higher concentrations can make the product feel more greasy or tacky to apply, especially on a hot and sweaty day.

Some organic filters are linked to endocrine-disrupting effects.

"An endocrine disruptor is a substance that changes the function(s) of the endocrine system and thus causes negative health effects"

Mainly benzophenones (ie oxybenzone), camphor derivatives and cinnamate derivatives are linked to endocrine disrupting effects. These UV filters are generally involved in the disruption of the hypothalamic-pituitary-gonadal system. Through animal experiments and cell studies, it has been possible to demonstrate that exposure to these chemicals provoked an endocrine-disrupting effect such as estrogen-like effects or androgen-like effects. The potential for hormone-disrupting substances is shown in table 1.

Some organic filters are also paradoxically sensitive to UV light. This means that they can break down in the presence of sunlight, which reduces their sun protective properties. In addition, in some cases, harmful substances can be formed that can cause allergies or other unwanted side effects. Some organic UV filters are suspected, or have been shown in models to be endocrine disruptors. The most skin-friendly and effective ecological or organic UV filters have a high molecular weight, which means they do not penetrate the skin. It is therefore of utmost importance to make a careful selection of UV filters and ingredients when formulating a good sun protection product.

Now we will dive deep into the organic UV filters. For a consumer, it can be difficult to read and understand the list of ingredients and which filters are used in the product because the filters have complex names. Also, the use and names of the filters may vary in different parts of the world. Several of the newer and better organic UV filters are restricted for use in the US which means that the US market uses many filters that have been phased out in Europe and most of the world, due to safety concerns.

Organic UVB filters

Aminobenzoates were among the first UV filters to be used but have more or less been phased out in Europe. The filter absorbs UVB but cannot absorb UVA. PEG-25 PABA is an effective UVB filter; however, it was reported, along with Benzophenone-3, as the most common photoallergen and contact allergen

Cinnamates replaced or supplemented PABA and are a potent UVB filter and include Ethylhexyl Methoxycinnamate and Isoamyl p-Methoxycinnamate. Ethylhexyl Methoxycinnamate is the most common UVB filter in the US and is still widely used in Europe. However, Ethylhexyl Methoxycinnamate is not very photostable and breaks down after a short time in the presence of sunlight, especially in combination with the UVA filter Butyl Methoxydibenzoylmethane. Ethylhexyl Methoxycinnamate is also considered an endocrine disruptor and has a negative environmental impact.

Salicylates are weaker UVB absorbers and therefore provide a lower increase in protection per added amount. They are also used to dissolve other UV filters and thereby increase the protective effect. Examples of these are Homosalate and ethylhexyl Salicylate. This group of substances is suspected of having endocrine-disrupting effects and is now being investigated for this.

Octocrylene is a very common organic filter and a relatively weak UVB absorber. The filter has widespread use but has been associated with phototoxicity and photoallergic potential. It is also considered an environmental pollutant and can cause coral bleaching.

Phenylbenzimidazole is a UVB filter that is a water-soluble compound typically used in products where you want a lighter, less greasy feel and when water resistance is not critical. Although the substance has been reported to cause photoallergy, it is considered to have a low risk of causing sensitization.

Ethylhexyl Triazone and Diethylhexyl Butamido Triazone are modern highly effective UVB filters with a large molecular size. Due to their size, they cannot penetrate the skin and are therefore not associated with skin allergy, skin reactions or endocrine effects. They are approved in the EU but not currently in the US. Used in Skinome Sun Emulsion.

Organic UVA and UVB filters with a broad spectrum

Benzophenones mostly absorb UVB. However, Benzophenone-3 is considered a broad spectrum filter because it also absorbs UVA. Of all the UV filters, however, Benzophenone-3 has the greatest likelihood of inducing contact or photocontact dermatitis and has therefore largely been phased out .

Bis-Ethylhexyloxyphenol Methoxyphenyltriazine is a modern UV filter that provides broad-spectrum protection and absorbs well in both the UVA and UVB range. The substance has a large molecular size and is not associated with allergies, an endocrine effect or skin reactions. Used in Skinome Sun Emulsion.

Methylene Bis-Benzotriazolyl Tetramethylbutylphenol (nano) is an organic particle filter that absorbs well in both UVA and UVB. Similar to titanium dioxide and zinc oxide, it will produce a white film when used in the product and applied to the skin. It has been associated with some skin reactions, but this may also be related to the additives used in the raw material.

Drometrizole Trisiloxane has a more limited use in specific brands. It has a larger molecular size and therefore stays on top of the skin and offers a limited risk of penetration and thus less risk of causing various skin reactions.

Organic UVA Filters

Butyl Methoxydibenzoylmethane has historically been the most widely used UVA filter. However, it is very photo-unstable, especially when used together with the cinnamates, which is also why its potency drops in contact with sunlight.

Terephthalylidene Dicamphor Sulfonic Acid and Disodium Phenyl Dibenzimidazole are photostable substances with a larger molecular size and also hydrophilic and therefore stay on top of the skin with limited risk of penetration.

Diethylamino Hydroxybenzoyl Hexyl Benzoate is a photostable modern UVA filter that has replaced Butyl Methoxydibenzoylmethane as the main organic UVA filter . This filter has no reported allergies or endocrine effects and is therefore considered hypoallergenic. Used in Skinome Sun Emulsion

Mineral filter

A common misconception is that mineral sunscreens protect the skin from UV light by reflecting and scattering the UV light. That is only partly true; they reflect UV light, but the bulk is absorbed in the same way that organic UV filters work. Most of the reflection occurs in the visible light that we see, which is why we see the (unwanted) white film on the skin.

Zinc oxide and titanium dioxide are the two approved mineral filters that are often combined to provide optimal UV protection. Zinc oxide, together with titanium dioxide, provides very good protection against both UVB and UVA, and also protects against longer UVA wavelengths (340 to 400 nm). Both zinc and titanium dioxide are very photostable and do not react with other UV filters.

Smaller particles, so-called nanoparticles, also provide better protection against the sun's UV rays than larger particles. Another advantage of the smaller nanoparticles is also that the white coating that mineral filters can leave on the skin is reduced. The smaller the particles, the less of a white layer the filter leaves on the skin. Although the nanoparticles are small, they are still too large to penetrate the skin, and much larger than most other substances and UV filters used.

There is an identified risk of inhaling the particles and therefore they are not used in spray products, but in creams they are perfectly safe. Since 2013, it is mandatory to label products containing nanoparticles in the EU. For example, a sunscreen may be labeled as follows: Zinc Oxide (nano).

 In summary, mineral filters cannot penetrate the skin but remain on the surface where they protect against the harmful radiation. Since mineral filters cannot penetrate the skin, the body is less likely to react to them than to the organic filters. Among other things, it is the low risk of allergies and the lack of hormone-disrupting effects that mean that mineral filters are often used in products for children and for people with sensitive skin. Both are used in Skinome's Sun Emulsion SPF50+ range.

Summary of UV filters in use today

The most common UV filters used in sunscreens are listed in Table 1.

Table 1. UV filters used in Europe. INCI stands for International Nomenclature of Cosmetic Ingredients and is the name given on the list of ingredients. Main absorbance defines the primary UV range within which the respective filter is active. The endocrine-disrupting effect and the risk of allergy is evident from table-based scientific evidence. 

How to choose the right sunscreen and how you should use it

When choosing a sunscreen product, there are countless options. To minimize the risks of being in the sun and to reduce the use of sunscreen, the best way is to dress properly and avoid the sun when it is high in the sky. But despite this, it is also important to regularly apply a sunscreen to the areas that are exposed. Preferably choose a product that protects against both UVA and UVB radiation and that provides high or very high protection. By choosing products that are fragrance free , you are doing yourself and your skin a favor as perfumes are among the most allergenic substances used in cosmetic products, an effect that can even be exacerbated by sunlight. To find the right product for you, it is good to think about:

  • What skin type you have. Fair-haired and red-haired people must protect themselves to a greater extent in order not to burn themselves.
  • How bright and strong the sun is . Check how high the UV index is in your area.
  • That your sunscreen gives you the right protection. Choose a product with a UVA symbol that ensures you get good, broad-spectrum protection.
  • Choose a photostable product that does not lose its effect when you stay in the sun.
  • Sun protection products with both mineral filters and new modern organic UV filters are best to ensure good protection against the sun.

To get the best possible sun protection, you should use at least as much of the product as the manufacturer recommends, as this is the amount that has been used when testing the product. A person's skin surface is usually estimated to be about two square meters and the amount of product used in the SPF tests is two milligrams per square centimeter. This is equivalent to about 40 ml for an adult body , which is more than most people use when applying sunscreen. A common standard used to get enough cream is to apply the amount that fits in a cupped hand to the entire body. If you use spray or mousse, it is much more difficult to understand how much is needed, as it cannot be quantified in the same way. In addition, it is best to apply a smaller amount to one body part at a time to get as smooth and even an application as possible.

A study has shown that sun protection increases significantly when the product is applied several times (Heerfordt, Torsnes, Philipsen, & Wulf, 2018). It's also easier to get a better application if you apply sunscreen before going out in the sun and starting to sweat. Of course, you also need to continually reapply the sunscreen product throughout the day. How often it's needed depends on how active you are and how much the product rubs off, but it's best to apply your sunscreen every two hours and always after swimming.

Clothes after weather

Clothing is the first line of defense we can take against the sun. In addition, wearing the right clothing can offer safer sun protection than sunscreen, since it is more difficult to apply sunscreen correctly (uneven application, too little amount, no reapplying). How do different items of clothing affect how well you are protected? How can you be sure that the garment effectively blocks the sun's rays?

Here are some tips:

  1. Dark clothes - black and navy, absorb more UV rays than lighter colors like white and pastels. For example, an everyday white cotton T-shirt has an SPF of only about 10. As a rule of thumb, you can think - the more intense the shade, the better protection the clothes will provide.

  2. Materials: Like color, the material, weave, and texture of your clothing can affect how well it protects you from UV rays. Synthetic and semi-synthetic fibers such as polyester or rayon are the best material choices for sun protection, as are dense, heavy, tightly woven fabrics such as wool, denim or corduroy. At the opposite end of the spectrum are lightweight fabrics (such as refined cotton), which tend to be thinner and allow more light to pass through. Example:
  • Shirt (Denim-jeans) SPF 1700
  • Blouse 100% viscose: SPF:15
  • White T-shirt 100% cotton: SPF 10
  1. Size : It's pretty obvious that the more skin you cover, the better protected you are from the sun's rays. However, it can be easy to forget that this also applies to hats! For the best sun protection, choose a hat that has a wide brim (3 inches or more) and with a tightly woven structure. A straw hat can cause the UV rays to penetrate through its openings. When it comes to sunglasses, choose a sturdy model with wide lenses that cover the eyes, eyelids and as much of the surrounding area as possible and make sure the sunglasses are properly fitted to provide complete protection from the sun's harmful rays. If the sunglasses slide down the nose, the risk of sun damage to the eyes increases.
  1. Loose fit: A loose fitting shirt provides a better SPF than a tight fitting one.