Does Sunscreen Break Down when Exposed to the Sun

[zeliciousz]

I'm not a chemist. I'm not in natural sciences at all. But recently, on a backpacking trip, my buddy and I got into a discussion and wanted to get an answer from someone who knew what they were talking about.

 

If I transfer sunscreen into a transparent container and put it in the sun, will the sun render the sunscreen impotent? Is it direct sunlight exposure that makes the sunscreen stop being effective? When I put it on my face, and it's exposed to the sun, it lasts an hour and then I have to reapply. If I store it in a transparent container, it is also exposed to the sun. Is that a bad idea?

 

Second part: If it does in fact render the sunscreen impotent, is it just the layer that is exposed to the sun, or does the sun radiation permeate to the rest of the sunscreen in the bottle?

 

Thanks for any input.

[John Cuthber]

It depends on the particular ingredients, but most are designed not to degrade in sunlight. They say you should re apply them regularly for 2 reasons.

On, they sell more that way.

2 the stuff is rinsed off by sweat and gets wiped off.

 

The outer layer of suntan stuff would protect the stuff inside the bulk of it.

[Iota]

I'm not a chemist. I'm not in natural sciences at all. But recently, on a backpacking trip, my buddy and I got into a discussion and wanted to get an answer from someone who knew what they were talking about.

 

If I transfer sunscreen into a transparent container and put it in the sun, will the sun render the sunscreen impotent? Is it direct sunlight exposure that makes the sunscreen stop being effective? When I put it on my face, and it's exposed to the sun, it lasts an hour and then I have to reapply. If I store it in a transparent container, it is also exposed to the sun. Is that a bad idea?

 

Second part: If it does in fact render the sunscreen impotent, is it just the layer that is exposed to the sun, or does the sun radiation permeate to the rest of the sunscreen in the bottle?

 

Thanks for any input.

 

I recently saw an experiment done by Cambridge University students, unfortunately I failed to retrieve it for you to see. Perhaps somebody can test it out? They first placed highlighter pen marks on their skin, then shone a UV light at the area. The reflection was strong and highly visible. They applied some sun screen over the highlighter marks, then shone the UV light at it again. The highlighter no longer reflected and was not visible in the dark room. This test was merely to demonstrate it works. Maybe someone could try it, then try it again; first on skin and then on a non porous/organic material, to see whether or not its effect wears out, at the same time, determine if its wearing is due to human skin or due to UV interaction with sunscreen ingredients?