physical vs. chemical sunscreen, proper to way apply sunscreen, why need to reapply sunscreen

Why use sunscreen? As a strong advocate of sun protection, I always include sunscreen as part of my patient education in the field of aesthetics especially amongst people who wanted to get rid of their sun spots, dark spots, melasma, or other related aesthetic issues. While lasers and IPL therapies can help address sun spots, they cannot prevent reoccurrence; thus I can’t stress enough sunscreen and other sun protection measures. The pathogenesis of melasma is not clearly understood; while it can be traced to genetics and hormones, sun exposure triggers overproduction of melanocytes, the cells responsible for melanin. There are many resources available on the internet when it comes to sunscreens and sun protections; there are differing opinions as to which offers the best form of protection thus I felt compelled to share my opinion. As always, my point of view should not replace your doctor’s. Do your research and settle for the one that conforms to your lifestyle.

Is it true that the higher the SPF, the more protected you are? No. The American Academy of Dermatology recommends at least SPF 30 which blocks about 97% of UV rays. There is no proof that higher SPFs can block 100% of UV rays or that you can stay out longer. The single most important thing to remember about sunscreen is REAPPLICATION every two hours (if staying out longer in the sun) or each time you get wet or sweaty.

What’s the difference between UVA and UVB? UVA (aging rays) has the longest wavelength and can penetrate the skin’s deeper layer. It contributes to photo damage (premature wrinkling), aging and immediate tanning. UVB (burning rays) has medium wavelength and is the main culprit to sunburn. Both UV rays contribute to melanoma or skin cancer.

I work in the office, do I still need to apply sunscreen? Yes. UV rays penetrate glass and windows. While some can filter UVB, you are still exposed to UVA rays. You drive going to the office, you walk going to the office, all these things contribute to sun exposure.

My makeup has SPF 20, do I still need to apply sunscreen? Yes. Unless you apply a dollop of makeup or 1 oz (shot glass) to exposed areas which is the recommendation to get adequate protection, then by all means you need to apply a separate sunscreen.

What kind of sunscreen should I use? cream, lotion, spray, stick? If you have dry skin, use cream-based. For oily and combination, use lotion. For small areas such as around the eyes, use stick. Personally, I avoid spray type because it is hard to configure whether you have applied enough. Sunscreen should be broad spectrum so you can get protection from both UVA and UVB.

How much sunscreen should I apply? The most common mistake people do is under-application, meaning we apply less than the standard recommendation. For my face, I do apply a dollop and for all other exposed body areas, at least an ounce or equivalent to one shot glass.

Which is better, physical sunscreen or chemical sunscreen? Physical sunscreen (zinc oxide, titanium dioxide) blocks the UV rays. There is no need to wait for 15 minutes before going out. However, it is deemed to be not cosmetically appealing because it’s harder to blend and leaves a white cast. Chemical sunscreen absorb UV rays which prevents it from penetrating the skin. It typically combines ingredients such as avobenzone, oxybenzone, octinoxate, octisalate to maintain its stability. The ingredients in chemical sunscreen are generally safe although there have been reported incidence of irritation (including myself). Bottomline, it all boils down to personal preference.

So what’s my favorite sunscreen to-date? Hands down, those physical sunscreens from eltaMD. I prefer the tinted version UV Elements SPF 44 because it has titanium dioxide and zinc oxide plus sodium hyaluronate for hydration. I use the sheer version SPF 45 for my neck, ears and other exposed body areas. Don’t forget your lips, currently I am loving Lather’s unscented lip balm which has broad spectrum SPF 15.

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15 thoughts on “Why Use Sunscreen?

  • What a fantastic, and very informative post, Kath! I need to add eltaMD to my list of sunscreens to try!

  • After reading your post the other day about eltaMD sunscreen, I ordered a sample last night to go along with the Mirabella mascara I ordered. Eager to try it out. My question and problem is how to reapply sunscreen on top of my makeup? I usually use a cream sunscreen (Coola, Exuviance, Marini, for example), and I apply my makeup on top of that. What to do when it's time to reapply my sunscreen? What do you do that doesn't smear or ruin your foundation etc?

    • Thanks Allison! Good question. When I know that I am spending longer time out, I skip foundation and just wear tinted sunscreen so it is easy to reapply. I lightly set it with a powder using a fan brush so it does not look cakey, that way it is also to reapply.

  • You have no idea how many times I've argued with people to tell them that NO, the SPF in their makeup isn't sufficient. They need a separate sunscreen.

  • I love your Q and A format. I think that you've done a great job talking about sunscreen. EltaMD is one I always wanted to try.

  • I used this brand a few years ago and really liked it!

  • This post is such an informative read!

  • Love hearing about these Elta MD products! What's your take on the UV Clear Broad Spectrum SPF 46? I've gone through more bottles of it than I can count, but lately have had some concerns and might switch. Firstly, the stuff isn't designed to last all day, so I'm unsure if I'm reapplying it enough. Second, I'm concerned about the niacinamide in it interacting with vit c. Thoughts?

  • Thanks for your questions. Are you reapplying it every 2 hours? That's how sunscreens are. Use a dollop too, I am very generous in application because most common mistake is under application. As for the interaction, I know there are several anecdotal resources on the internet that say you can't mix it. Unfortunately there are very limited clinical studies in the realm of skincare. I use Vitamin C and another eltaMD sunscreen w/o niacinamide in it, you may want to explore that

  • Well the vit c/b info is a bit confusing right now, so maybe it is best to separate them. I usually just reapply sunscreen around lunch when I'm indoors all day. It doesn't seem like enough, but reapplying every 1-2 hrs from dawn til dusk is gonna be a tough lifestyle adjustment. I'm confident that I apply enough- 1 pump of the spf 46 is ~a teaspoon. It's easy to reapply something like colorscience powder every hour, but it's usually not a full application. Maybe I need to peruse some of the light as air Japanese sunscreens. There are way worse problems to have- thx for the advice!

  • Reapplication every 2 hrs is when you're staying out longer in the sun or whenever you get wet or sweaty. Yes, you can space out Vit C and Niacinamide. In the morning, I apply Vit C and eltaMD Barrier Complex, have coffee (I spend 30 mins looking over emails, etc) then prepare to get ready for work. That's when I apply sunscreen

  • Cool, thx for the guidance! So nice to have all these great products to work with.

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