Mineral sunscreens - why do they leave a white cast?

Have you ever wondered why some sunscreens leave a white residue on your skin? So have we! In this article, we explain how the "whitening effect" occurs and why it is particularly common with mineral sunscreens.

Contents:

What is the whitening effect?

First, it's important to understand that there are two different types of UV filters used in sunscreens: organic ("chemical") filters and inorganic ("mineral") filters. While organic UV filters penetrate the skin and convert UV radiation into heat, inorganic UV filters contain particles that reflect, absorb, and scatter light.

Okay – let's explain that again, slowly: Mineral UV filters form a film on the skin when applied, creating a physical barrier that protects the skin from the sun's rays. The particles from the mineral UV filters reflect the sun's rays like a mirror, remain on the skin, and thus cause the so-called whitening effect. But why white?

Good to know : When light hits a surface that reflects all colors of the light spectrum, we see "white" - and that's why the skin appears "whitewashed" after applying a mineral sunscreen.

How do I know if a sunscreen is mineral-based?

The easiest way to determine if your sunscreen is mineral-based is to carefully examine the product description and packaging. Pay close attention to the list of ingredients (INCI). Mineral sunscreens primarily use the UV filters zinc oxide or titanium dioxide. Chemical UV filters often have very long, complicated names such as Ethylhexyl Salicylate, Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine, Diethylamino Hydroxybenzoyl Hexyl Benzoate (DHHB), or Octinoxate. In certified natural cosmetics, the use of these chemical UV filters is prohibited.

Which sunscreens do not whiten?

Sunscreens with chemical filters generally do not have a whitening effect because they do not form a protective barrier on the skin, but rather work deeper within the skin cells. However, due to the chemical filters used, they are often harmful to health or the environment and require a certain absorption time to provide full UV protection. Mineral sunscreens work immediately and do whiten, but there are significant differences in the intensity of the whitening effect. This is mainly due to the amount of filter used, the size of the filter particles, and the other ingredients in the sunscreen.

What does "nanoparticle-free" actually mean?

First, we should state that sunscreens with mineral UV filters are never completely free of nanoparticles. When zinc oxide is broken down, particles of all sizes are created—similar to a glass bottle that shatters into fragments of varying sizes. Even with a zinc oxide sunscreen that states "non-nano" on its packaging, you will find individual nanoparticles. "Non-nano" only means that less than 50% of all zinc oxide particles are of nano-size—as stipulated by the European Commission.

According to these guidelines, our sunscreens with zinc oxide are not considered a filter with nanomaterial, but individual particles are still present in nano-size. So, all our sunscreens contain nanoparticles. However, in recent years, nanoparticles have often been unfairly condemned across the board. When it comes to whether nanoparticles are good or bad for the skin, it's not just about the size alone, but primarily about which substance is present in nano-size and whether it is "biopersistent," meaning it can remain in the skin. And this is not the case with our sunscreen, which only contains zinc oxide particles. Feel free to read here what the Ärztezeitung (Doctors' Newspaper) says about the safety of zinc nanoparticles!

You definitely need to know this!

Sure, the whitening can be annoying in some places – but look at the positive side: especially with children, you can easily see where they have already been creamed and where they haven't. Please also make sure that you do not apply the mineral sunscreen extra thinly to avoid the whitening effect. Sufficient sun protection is especially important for the health of our children! 