Dr Irwin : Sunscreens

Tips from Dr. Irwin on why SPF doesn’t tell you everything you need to know about a sunscreen. And what ingredients to look for in a sunscreen to block UVA as well as UVB radiation.


This is Dr. Brandith Irwin in Seattle at Madison Skin and Laser Center and this is a video blog for skintour.com.

I want to talk today about sunscreens. Why are they so confusing? And there are thousands of them, right? And why are there so many? Do we really need them all? And “what is it I should be looking for” is what I hear from my patients a lot. Here are the basics.

Basically, SPFs are confusing. The reason for that is the SPF only tells you how long can you be out in the sun, how much longer can you be out in the sun without burning. It really doesn’t tell you what total percentage of UV light is the sunscreen blocking. In other words, if you normally would burn in an hour out in the sun, an SPF 15 allows you to stay out for 15 hours. Well, OK. How many of us are out for 15 hours? But what it doesn’t tell you is how much UVA it’s blocking. The reason is the SPF ratings only refer to UVB, not UVA. And we don’t have a rating system for UVA. Isn’t that crazy? I think so because now a product can say broad spectrum on it, covers UVA, and have only the most minimal of UVA coverage in it. So now you think, OK, I’m buying this SPF 45 sunscreen; this should be great right, and it says broad spectrum on it so I’m covering UVA right? Maybe not. In fact it might be covering most of the UVB and almost none of the UVA depending on exactly what active ingredient it had in it.

I’m really encouraging my patients to start reading their labels. Here’s what you want to look for in your sunscreen. You want to make sure you have at least an SPF 15 and frankly, if you are going to be out all day water skiing, get something that’s higher. Get a 45 just because it might not wash off quite as quickly. Make sure it’s waterproof or water resistant and then make sure that it covers UVA. The way to do that is to look at the label. You want either zinc or titanium dioxide…or titanium, sorry, you want zinc or titanium 5 to 10% on that label to have a really good sunscreen or you want mexoryl 3%. Mexoryl you may have read about. It’s the new UVA blocker that’s been available in Europe and Canada for years. And so one of those three things will do it. As long as you make sure it says that, all of them block UVB pretty well and that way you’ll be sure you’re covered.

So, read the ingredients, most of the time the labels don’t tell you what you really need to know.

Dr. Brandith Irwin, MD

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Hi, I’m Dr. Irwin, and I believe that consumers need and deserve a medically trained and unbiased skincare advocate.

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