The first rule of applying sunscreen – The spf’s of various products don’t add up!!! If you are applying a moisturiser with spf, say x, then a sunscreen / foundation / BB cream with spf, say y, and then finish off with a mineral compact which again provides some spf, say z, factor, you can’t say that the sum total of your sun protection factor is spf x+y+z.
But, something else bothers me in this rule!!! Well, when we have layers of product with spf factors, x, y or z, which spf does apply on the skin – x, y or z? Or, does it work like a filtering mechanism? Meaning, if supposing the top layer has spf of z, those many rays are allowed to pass (remember even 50 spf allows 2% sun rays to pass through, it provides around 98% protection!!). And, then, the next product spf, which is y, again filters out the rays according to its strength and so on!!
Does that happen at all? Well. logically speaking, it does seem quite probable but I don’t know how much of that really applies in practice. Would be great if some sunscreen expert can answer such questions!!! What are your thoughts on it?
Indu indgal says
April 16, 2012 at 7:06 PMNice post. I think the same too. Maybe the product with highest SPF will give better protection I guess. Maybe we should ask a dermo
Swati Murti says
April 17, 2012 at 7:36 AMhey Indu….yup sunscreens have so many myths and questions that we really need them to be answered by someone knowledgeable!!!
Divine Blush says
April 17, 2012 at 3:28 AMdear plz do tell me whther.. we can apply sunscreen directly or we have to mix a bit of moisturizer and apply it..??
My way is – I use to apply Laco Calamine with my suncreen is it good..
Swati Murti says
April 17, 2012 at 7:38 AMno, I think its always better to use sunscreen as a stand-alone product…if you need to apply moisturiser, apply a very thin layer of it first as soon as you come out of the shower and wait for 10-15 minutes to let to absorb completely. then, after your skin entirely dry and free of water, follow with proper amount of sunscreen for adequate protection.
do you use lactocalamine under your sunscreen? or, mix your sunscreen with lactocalamine?
Divine Blush says
April 18, 2012 at 4:36 AMI ll mix lacto calamine with my sunscreen.. it doesnt show any reaction in my skin.. but on the last sunday i tried applyng sunscreen directly on my skin ..I got pimples.. I dnt know whether it is bcoz of the sunscreen or bcoz of the heat..
ray says
April 17, 2012 at 9:51 AMits true layering the products containing SPF do not add up to give protection against your skin….foundations & moisturizers contains other chemicals which can present sun blocking substances from working. read the ingredients in your sunblock.true sun blocking substances like zinc oxide & titanium oxide don’t get absorbed in the skin & help protect it from the sun
Swati Murti says
April 17, 2012 at 10:07 AMhey Ray, yes, I do prefer zinc oxide in my sunscreen but sadly, its not available in India 🙁 and, I do prefer to use stand-alone sunscreen instead of foundations and moisturisers having spf….do take a look at my sunscreen posts, your views are highly appreciated 🙂
perfectskincareforyou.blogspot.in/search/label/sunscreen
ray says
April 17, 2012 at 12:16 PMSkinkare contains zinc dioxide, UVDERM contains titanium dioxide.These re not marketed commericially. Try in a medical store nearby. I use UVDERM
ray says
April 17, 2012 at 3:40 PMI ll checkout & tell.I got it as a sample actually. The name of the product is SkinKare.Its from a pharmaceutical company
Swati Murti says
April 17, 2012 at 12:24 PMoh wow!!! can you give me the complete name of the skinkare product!!! I prefer Zinc oxide over Titanium one. So, I’ll definitely try to get it 🙂
Divine Blush says
April 18, 2012 at 4:39 AMthanks dear for sharing the names.. does it make skin oily ..
ray says
April 17, 2012 at 12:23 PMmy god!!! you ve done lots of post on sunscreens.my friend was planning to do his thesis on sunscreens so i know a quite about it.you ve done a wonderful work with sunscreen
Swati Murti says
April 17, 2012 at 12:44 PMhaha…yes, I have read about a lot!!! but, I have soooooo many questions 😀 wow…your friend is such a valuable resource!!!
Eco Beauty Vivi says
April 17, 2012 at 9:17 AMHi Swati, from what I’ve read, only the layer with the highest SPF will make a considerable difference. And once you layer them, they don’t really filter UV rays per layer, they sort of act as just one layer. The only advantage from layering products with SPF is that you get to apply more sunscreen than you would usually do if you were only applying one product.
But it’s not recommended to layer physical and chemical sunblocks on top of one another as the ingredients might react with one another and destabilize the formulation.
Swati Murti says
April 17, 2012 at 10:04 AMthanks a lot Vivi for clearing that up 🙂 yes, definitely physical and chemicals should not be mixed!!!
Rae says
April 26, 2012 at 12:58 AMHi, spf doesn’t add up. But many dermatologists agree that it is a good thing to apply both chemical suncscreen and physical sunblock on top of each other. Ignore first your question on which SPF applies. A good way to think about it is, when the physical sunblock ingredients reflect the light, whatever else that tries to pass through is absorbed by chemical sunscreen.
Also, it’s a good thing to layer, because the SPF rating ONLY holds true for a specific amount of product over a specific area of skin. Specifically, 2mg for every 600cm2 (cm-squared). And, it’s almost always unlikely to put that amount of product on the face. Example, you would need 1/6 of a whole pan of powder foundation on your face for the SPF rating to hold true. Layering increases the amount of product on your face. At least, in some ways that helps. Here’s a good reference: The ugly truth about moisturizers and makeup with SPF.
The only problem left is all this mixing and layering can make the skin react negatively.
Hope this helped,
Rae
Swati Murti says
April 26, 2012 at 11:57 AMhey Rae…thank you so much for the detailed reply 🙂 so true that we can’t really use that much of product on the face!!! didn’t know that 16th of the pan will give that much…this is why I really prefer physical blockers…they just perform better because chemical blockers have stability issue too.
Rae says
April 28, 2012 at 8:29 PMAnd that. Also, almost all sun protection ingredients induce free radical formation once they get exposed to sunlight. Especially chemical blockers. It just so happened that the benefit of sunprotection exceeds the free radical formation side effect.
The only ingredient I know that doesn’t react to sunlight is zinc oxide.
Swati Murti says
April 29, 2012 at 4:09 AMyes, that’s the only reason I am searching for a Zinc Oxide sunscreen…have been using Marie Veronique but it turns out too expensive so checking out if there is a similar product in lesser price!!!
but, neutrogena’s helioplex is a stabilizing technology that doesn’t let avobenzone and oxybenzone breakdown in the sunlight and hence, hopefully, the don’t produce free radicals!!! its ultra sheer is definitely a good product. but, its Zinc Oxide for me at the end of day 🙂
Rae says
April 29, 2012 at 2:06 PMIf you have Jason or Alba there. Both of them have purely mineral sunscreens. (no other sun ingredients except for zinc oxide, some of them have a little titanium dioxide.
Swati Murti says
April 29, 2012 at 2:55 PMno, unfortunately, Rae…in India, we have none of them…have to be ordered online…we do have soleo organics…its from Australia but its way too thick and heavy!!!
Anonymous says
May 31, 2012 at 6:29 AMWhat about mexoryl? How is it compare to zinc oxide?
Swati Murti says
May 31, 2012 at 9:21 AMhey…I have already written about mexoryl. You can read it here: http://perfectskincareforyou.blogspot.in/2011/09/sunscreen-ingredients-sunscreen.html
scroll down a bit and you will find it 🙂