Photostability refers to a products ability to retain its integrity when exposed to light. Just like our skin, the world around us is subject to degradation from the usual things like free radials, the environment, oxidation and UV exposure. Thus, many products need to consider their photostability to ensure they're actually effective and/or long-lasting.
What is a Photostable Sunscreen?
When something is photostable it means it's 'resistant to change under the influence of radiant energy and especially of light.'
And as we know, the inherent purpose of SPF is to stop UV damage and degradation, so if you want your SPF to properly protect you from the sun, then you want it to be photostable.
Why do I want my SPF to be Photostable?
- To ensure the product doesn't degrade on your skin and prevent it's purpose
- To ensure the product doesn't degrade in it's packaging and prevent it's purpose before use
- To ensure the longest life for the product whilst still effective
An SPF that isn't photostable heavily relies on other sun protection factors such as hats and full length clothing to safe guard their integrity.
How to Know if my SPF is Photostable.
Sunscreens and sunblocks do not have to list whether they are photostable or not. So here's what to look out for.
The key active/s in your SPF will tell you if it's photostable or not.
One of the most popular active SPF ingredients is avobenzone, but studies show it degrades rapidly when exposed to light on its own. In the graph above, you can see that Avobenzone protects you from UVA rays, but the fact it isn't photostable drastically increases its ability to do so.
The main SPF actives that are not photostable are:
In adequate concentrations, the main SPF actives that are photostable are:
- Mexoryl XL
- Zinc Oxide
- Titanium Dioxide
Studies proving Zinc Oxide to be a photostable active gave us another (amongst countless other) reasons to make Zinc Oxide the key active in Super Sun SPF50. As well as being a mineral active, its photostability means that the broad spectrum protection (UVA and UVB) it provides isn't impaired like it is in avobenzone. Making Super Sun the photostable, broad spectrum SPF50 of your dreams.