Can applying SPF harm more than it helps?

simmmchen

simmmchen

✯ mathemagician ✯
Nov 4, 2006
2,657
4
#1
"recent research at the University of California indicates that sunscreen needs to be reapplied within 2 hours in order to remain effective. Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from absorbed chemicals." (Wikipedia)

OMG, this really has me worried!

I have only recently started using sunscreen on my face every day, but I only apply it in the morning and then midday, if I am outside a lot. But this sounds like we have to apply it every 2 hours to prevent cell damage. And what about when the sun has set? Do we need to clean our face immediately in order to prevent damage form the absorbed chemicals?

What do you think? :shrugs:
 
#4
titanium oxide won't be absorbed into the skin and it will last as long as the cream is not rubbed off. It's actually a white pigment that reflects the sun. It's mostly in sun block I think, not in most sun screens.
 
#5
Wikipedia is not a credible source for that kind of information, or for any kind of information for that matter. Studies show this, studies show that, but nothing like what you're hearing has ever been proven. Keep in mind this is just one study. What I do know is that the higher SPF you wear, the longer the sunscreen lasts. My dermatologist actually recommends at least an spf of 30 rather than the nationally recommended 15. I actually notice many lotions and sunscreens racking their SPFs higher these days. As far as the study is concerned, I wouldnt worry too much about that. To me that sounds absolutely ridiculous. Nobody can reapply sunscreen every 2 hours and researchers know that.
 
#9
I know Wikipedia is not 100% reliable, but neither are all derms when it comes to recent studies! No doctor can know everything, esp not when it is a fairly new study! (this one is not even a year old!)

Anyway, here is a summary from the actual study (not from Wikipedia!):
The number of UV-induced (20 mJ cm−2) reactive oxygen species (ROS) generated in nucleated epidermis is dependent upon the length of time the UV filter octocrylene, octylmethoxycinnamate, or benzophenone-3 remains on the skin surface. Two-photon fluorescence images acquired immediately after application of each formulation (2 mg cm−2) to the skin surface show that the number of ROS produced is dramatically reduced relative to the skin − UV filter control. After each UV filter remains on the skin surface for t = 20 min, the number of ROS generated increases, although it remains below the number generated in the control. By t = 60 min, the filters generate ROS above the control. The data show that when all three of the UV filters penetrate into the nucleated layers, the level of ROS increases above that produced naturally by epidermal chromophores under UV illumination.
Click to expand...
read it here
(ROS are free radicals)

So... they are naming the *bad ones*: octocrylene, octylmethoxycinnamate, or benzophenone-3 ...
 
#10
My daughter uses Shiseidos new SPF 55 and she loves it. She also uses the face one they have, I think thats SPF 35. I am very fair and dont go in the sun, but I do put SPF on my arms and face, just driving causes sun damage.
 
#13
I use moisturizer with SPF30 every day i only put it on once a day since i dont go outside much at all, you only have to reapply if you spend most of your time outdoors.
 
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