Contents / Sommaire
- 🇬🇧 What makes a broadspectrum sunscreen?
- 🇫🇷 Les ingredients d’une crème solaire à large spectre
Sunscreens are a must if you want to prevent photoaging and skin cancers.
As soon as sunny days come back, you might consider using a sunscreen again. But do you know how they actually work? This series entitled Sunscreens and Your Skin answers the question. It follows the Ultraviolet Rays and the Skin series.
In this first part, we’ll dig into what broadspectrum sunscreens means and what kind of UV filters industrials use.
In the other articles from the series, I have discussed:
- in Part 2, about the differences between organic (or chemical) and inorganic (or physical) sunscreens as well as about micronisation (reduction of inorganic filters into nanoparticles), especially to avoid white cast.
- in Part 3, about the meaning of SPF, PPD, PA+… labeled on the packaging of a sunscreen.
In the Ultraviolet Rays and the Skin series, I have discussed:
- in Part 1, about the sunlight and introduced the UVA, UVB and UVC rays,
- in Part 2, about the effects of the sunlight on the skin in a timeline showing that UV exposure has beneficial and deleterious effects and leads, in the worst case to skin cancer.
- in Part 3, about how to enhance your natural skin protection against UV rays.
–– Why does a banana wear sunscreen? Because it peels. ––
The skin is one of our largest organs. Hence, protecting it from ultraviolet radiation (UVR) is crucial to prevent short and long-term skin disorders. When choosing a new sunscreen, selecting one with broadspectrum proprieties is a must.
🇬🇧 What makes a broadspectrum sunscreen?
1. You said broadspectrum?
Since UVA and UVB radiations that hit Earth’s surface range from 290 to 400nm (nanometer), sunscreens available in the commerce must have a a wide-range coverage to ensure protection against them (1). Sunscreens protecting from both harmful UV rays are called broadspectrum. Otherwise, they can lead to wrinkles, sunburns, skin cancers and immunosuppression disorders (2).
This protection is done by the filters contained in the product. There are two types with different properties which are used to ensure broadspectrum protection: chemical (organic) and physical (inorganic) filters. Commercial preparations available in the market include a combination of these agents to cover a wide range of UV rays.
2. Composition and mechanisms of action
- chemical UV filters are organic molecules (usually containing a carbon atom linked to a hydrogen one) absorbing UV radiation within a specific range of wavelengths depending on their chemical structure and releasing the energy as lower-energy rays or by vibrating, thus preventing the UV radiation from reaching the skin. They can be referred to as chemical absorbers.
- Inorganic filters reflect, scatter and absorb UV rays: they contain inert minerals such as titanium dioxide or zinc oxide (3). They can be referred to as physical blockers.
3. Filter proprieties in UVA and UVB
As you can see in image 3, some organic filters absorb only in the UVB radiation, others only in the UVA spectrum and some are broadspectrum like Oxybenzone (widely used in the USA), Mexoryl XL and Tinosrob M (used in Europe and Asia). Titanium and zinc dioxides are also broadspectrum.
As mentioned earlier, in real life, to ensure maximal photoprotection (protection of the skin from deleterious radiations), organic filters can be combined with those inorganic or sunscreens with only organic agents (respectively inorganic) can be formulated (4).
Are filters which absorb in the same range equal? That is actually not the case as seen below.
Despite having the same range of absorbance, Titanium (TiO2) and zinc (ZnO) dioxides don’t have the same efficacy: TiO2 absorbance is strong in the UVB range and then depletes around 360nm whereas ZnO absorbance peaks in the longer range of the UVA, thus, prompting sunscreen companies to use both as complements.
4. What to remember
Choose a broadspectrum sunscreen protecting against UVA and UVB radiations; it is usually mentionned on those with controlled labels:
- UVB protection is indicated with an SPF (the higher, the better photoprotection it gives against those rays)
- and depending on your country, UVA protection can be pointed out with a PA factor (number of +) in Asia, a PPD factor (number) in Europe or simply with UVA in Europe or broadspectrum terms in the US. If you have a PPD or a PA factor, the higher the number or the number of +, the better protection you get.
- Those products usually contain a combination of organic and inorganic filters. They also can have full organic or full inorganic filters. For consumers, combined or full-type filters come with benefits and drawbacks.
In the next part, I will compare those sunscreens. I am also writing an article about the labels on the sunscreens so that you will be able to choose them easily wherever you are :).
Do you know if your sunscreens are broadspectrum? Leave a comment