# Sunscreen **URL:** \ **Category:** Factual Questions\ **Created:** [June 15, 1999, 12:37am UTC](https://boards.straightdope.com/t/sunscreen/1095 "1999-06-15T00:37:00Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 15, 1999, 12:37am UTC](https://boards.straightdope.com/t/sunscreen/1095/1 "1999-06-15T00:37:00Z")
No, this isn’t about that graduation speech. 😉 Being fair skinned, and especially susceptible to burning, I, in an ongoing obsessive-compulsive quest to avoid all types of skin damage, wear sunscreen every day (though I do not spend much time in the sun.) Well, the bottle (of sunscreen) says that I should re-apply after every eighty minutes of swimming or sweating, and every time I towel off. But, I don’t usually do these things; I sit in a classroom for six or seven hours, then stand outside for about an hour waiting for my ride home. (I put on the sunscreen in the morning when I get ready for school.) So here’s the question: Do you think I need to re-apply sunscreen after sitting in an air-conditioned building from 8 - 2? Or should it still be working? * * * The mass of men lead lives of quiet desperation. – Henry David Thoreau ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 15, 1999, 12:42am UTC](https://boards.straightdope.com/t/sunscreen/1095/2 "1999-06-15T00:42:00Z")
I suspect that under the conditions you describe there will be no measurable difference (in aging, skin cancer, etc.) between reapplying and not. ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 15, 1999, 3:30am UTC](https://boards.straightdope.com/t/sunscreen/1095/3 "1999-06-15T03:30:00Z")
I hate to admit it, I should know this by now, but I really haven’t figured out if the current sunscreens go bad on standing for a year.Anyone have the facts? ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 2:09pm UTC](https://boards.straightdope.com/t/sunscreen/1095/4 "1999-06-16T14:09:00Z")
I might be able to help on the sunscreen expiration. I worked in a lab that tested sunscreens (among other things) for their chemical composition and potency. It is common practice to get samples of sunscreen from the manufacturer, test them, and other samples for stability studies. After several months or a year, we test the stability samples. I have found from personally testing these sunscreens that the chemical potency does not degrade significantly after a year. I use these stability samples myself and have one labeled (expiration date 6/97) which worked as of last week. No doubt, the chemicals will degrade significantly, given enough time and I’m sure the 1 yr expiration date is probably more for legal protection (so some yutz doesn’t sue after getting fried while using 30 yr old sunscreen), but I have no problem using the stuff I’ve tested that is a few years old. ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 2:29pm UTC](https://boards.straightdope.com/t/sunscreen/1095/5 "1999-06-16T14:29:00Z")
Thanks.Always an expert here! ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 3:43pm UTC](https://boards.straightdope.com/t/sunscreen/1095/6 "1999-06-16T15:43:00Z")
Cess, why not get an umbrella? They look pretty intelligent these days. Putting on sunscreen also adds this stuff to your body and you might find an umbrella to be much better if you are going to use it a lot: benzophenones dixoybenzone oxybenzone (not water soluble) PABA and PABA esters ethyl dihydroxy propyl PABA (not water soluble) glyceryl PABA (not water soluble) p-aminobenzoic acid (water soluble) padimate O [octyl dimethyl PABA] (not water soluble) cinnamates cinoxate ethylhexyl p-methoxycinnamate octocrylene octyl methoxycinnamate salicylates ethylhexyl salicylate homosalate (water soluble) octyl salicylate ``` MISCELLANEOUS avobenzone [butyl-methyoxydibenzoylmethane; Parsol 1789] digalloyl trioleate menthyl anthranilate PHYSICAL red petrolatum (not water soluble) titanium dioxide zinc oxide (not water soluble) ``` ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 3:54pm UTC](https://boards.straightdope.com/t/sunscreen/1095/7 "1999-06-16T15:54:00Z")
Bill: I’ve heard than anything over 30 in sun protection factor is overkill. Any truth to this? ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 9:40pm UTC](https://boards.straightdope.com/t/sunscreen/1095/8 "1999-06-16T21:40:00Z")
> [@](#): > > Cess, why not get an umbrella? They look pretty intelligent these days. Putting on sunscreen also adds this stuff to your body and you might find an umbrella to be much better if you are going to use it a lot But are any of those chemicals actually bad for me? * * * The mass of men lead lives of quiet desperation. – Henry David Thoreau ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 10:59pm UTC](https://boards.straightdope.com/t/sunscreen/1095/9 "1999-06-16T22:59:00Z")
As long as we’re on the subject of sunscreen, occasionally in the privacy of my bedroom I use sunscreen not as a moisterizer but as a–er–lubricant. Is there any danger in this? ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 11:45pm UTC](https://boards.straightdope.com/t/sunscreen/1095/10 "1999-06-16T23:45:00Z")
Don’t see any point to it, Ed. Specially given that you’ll go where the sun don’t usually shine 😃 ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 16, 1999, 11:52pm UTC](https://boards.straightdope.com/t/sunscreen/1095/11 "1999-06-16T23:52:00Z")
Does sunscreen actually _work_ for that, Ed?!? Actually, I think you should check out the label on the bottle, mine says not to let it come in contact with the eyes or mouth. I would assume that. . . other areas may be equally sensitive. * * * The mass of men lead lives of quiet desperation. – Henry David Thoreau ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 17, 1999, 12:54am UTC](https://boards.straightdope.com/t/sunscreen/1095/12 "1999-06-17T00:54:00Z")
Let me be more specific–I am **NOT** talking about my butt. I just use it to reduce friction in–other areas. Boy do I feel stupid in bringing this up… ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 17, 1999, 1:16pm UTC](https://boards.straightdope.com/t/sunscreen/1095/13 "1999-06-17T13:16:00Z")
Butt ain’t the only place where the sun don’t shine, Ed 😃 ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 17, 1999, 3:21pm UTC](https://boards.straightdope.com/t/sunscreen/1095/14 "1999-06-17T15:21:00Z")
Butting in here, Handy: PABA is no longer used. I forget why. ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 17, 1999, 3:36pm UTC](https://boards.straightdope.com/t/sunscreen/1095/15 "1999-06-17T15:36:00Z")
Just make sure you check that sunscreen for petroleum distillates, Ed… they can adversely affect the wear characteristics of those latex chaps. =: ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 17, 1999, 7:02pm UTC](https://boards.straightdope.com/t/sunscreen/1095/16 "1999-06-17T19:02:00Z")
Thank you bill for dispelling that common disagreement I’ve had with many who think you have to throw out your sunscreen after a year. These are the same schmoes who actually throw out plant and veggie seeds after a year because they think they expire. Sheez…I have flower seeds from 1992 that are still spouting. * * * WE are all pilgrims on the same journey - but some pilgrims have better road maps. ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [June 17, 1999, 9:15pm UTC](https://boards.straightdope.com/t/sunscreen/1095/17 "1999-06-17T21:15:00Z")
I think I’ve found an answer to my question, and APB9999, I think you were wrong. I’ve been putting on sunscreen before class everyday for a week, yet I still seem to be getting a tan; I’m even red in some spots. Guess I’ll have to try something new. I like the winter so much better; it’s still sunny, but at least it’s cool enough that I can wear long sleeves. * * * The mass of men lead lives of quiet desperation. – Henry David Thoreau