UV Cameras: Can you Use them To Tell You if your Sunscreen is 'Good' or 'Bad'?
Do UV Cameras work for sunscreens?
Here is the trending question of the day: do UV cameras work for sunscreen? Can they tell you how strong your sunscreen is? If it’s ‘good’ or ‘bad’ or can you use it to compare different sunscreens and the strength of their UV protection… The short answer is no.
People are going crazy over these UV light and sunscreen application videos, especially as they trend on TikTok, but here is the issue. UV cameras are not designed to show you the strength of your sunscreen’s performance and here is why.
The Physics of a Woods Light and UV Cameras
First- what is a UV camera and how does it work? There are a couple of different options available from ones that can be used in your dermatologists office to take home ones you can buy online. A Woods light as used in dermatology offices is to diagnose lots of disorders like melasma, skin fungal infections and much more. It’s a weak form of UVA light in the range of 320 to 400 nm wavelength. Importantly, it peaks at 365 nm. I have no idea if the UV cameras that you can buy for home emit the same wavelength of light or what the absorption is, unfortunately, they don’t share a lot of details in their product descriptions. It’s probably a safe assumption they are using similar wavelengths of light but they may not be standardized across different models, nor are they regulated.
Why does sunscreen show up dark on a UV camera?
So the idea is that you put a sunscreen on and you can see where you are applying it because it shows up as darker. Why? Basically the photons of UVA light are sent out, pigmented skin and sunscreens (at least some) absorb the light and send back light as visible light, ie fluorescence, ie it looks darker. Your skin reflects and scatters light and therefore doesn’t appear as dark by contrast.
Why does this not work for all sunscreens?
The issue is that it’s known that mineral sunscreens and tinted sunscreens don’t always light up or look as dark as other sunscreens. Why? Is it because they aren’t as ‘strong’ as ‘chemical’ filters? No.
Mineral filters but also other ‘particulate’ grade filters, like Tinosorb M (MBBT), work mostly by absorbing UV light, which is why we should stop calling them ‘physical’ versus chemical filters. However they do also work by light scattering and reflection just to a lesser degree. Unfortunately, we do not know the degree of light scattering and reflection anyone version of these filters might be doing. It’s challenging to quantify and there might be differences between the different dispersions of filters as they are supplied by different raw material manufacturers. We simply do not get this type of information as a brand and it’s generally deemed propriety to the supplier.
This means that if you are using a mineral sunscreen, a tinted one or perhaps even one with particulate grade filters like Tinosorb M or Tinosorb A2B and it doesn’t ‘light’ up, i.e. look darker, on the UV camera- you don’t know if it’s because it’s a poor sunscreen or if it’s because of a factor like light scattering and reflection. There are too many unknowns and for this reason- you really should not use it to judge the strength of your mineral or ‘chemical’ sunscreens.
UV Camera’s are not well studied and many questions are unanswered
There are so many unknowns when it comes to using a UV camera and sunscreen and there is little in the way of current studies to support any firm conclusions. For example, I also wonder if UV filters that have strong absorption in the 340-365 nm, where the Woods light is selectively stronger and focused, does that mean that UV filters like Avobenzone or Uvinul A Plus will show up as darker? Remember, that’s the very specific range of UV light where they are performing the best before they fall off in the longest UVA wavelengths and visible light. Are UV cameras literally just showing off certain filters in their best light?
Is it a coincidence that particulate grade filters like zinc oxide and Tinosorb M work so effectively in the blue light range because of their light scattering properties also don’t flouresesce as strongly because of these same properties? Ie because of their strong performance in visible light does it impact their visible performance in a UV camera? Also keep in mind tinted sunscreens that use titanium dioxide or iron oxides will have the same issue.
How should I use my UV camera?
Those are all questions that need to be asked and until they are, you cannot and should not use a UV camera to tell you the ‘strength’ of your sunscreen. What can you use it for? Purely to tell you if you missed a spot in applying your sunscreen. You should not even use it to see if you have applied enough on as one study showed that 1 mg/cm2 looked the same on camera as 2mg/cm 2. I would also caution against using a device that emits a low amount of UVA light every single day. It’s a different issue when your dermatologist uses a Woods light to diagnose a skin condition and exposes your skin for 2-5 minutes. It’s a separate issue when you are exposing yourself every day and potentially multiple times of day, for a limited benefit. Something to consider before you purchase one for home use. At The Sunscreen Company, we love to offer the best in continuing skincare and sunscreen education, so make sure to follow us on IG @thesunscreencompany.