Wednesday, April 7th, 2010


Disclaimer: I am not a doctor, licensed esthetician, skincare expert, etc. This is information I have gathered from reading many different sunscreen-related articles throughout the past few years. I’ve provided links for reference purposes. As always, please consult your doctor and/or dermatologist for the latest and most accurate, up-to-date information.

Why sunscreen?

Wearing sunscreen will help prevent your skin from burning from harsh UVB rays and reduce the effects of UVA rays on the deeper layers of your skin–it may help reduce the signs of aging later on down the road as well as lower your exposure risk to skin cancer.

What are UVA and UVB?

  • UVA rays are the kind that have the greatest effect on you… that you don’t necessarily see right away. This includes aging and wrinkles as well as increase the risks of skin cancer.  Think of UVA as the AGING (and cancer-causing) rays.
  • UVB rays are the kind that you’ll notice right off the bat,  because UVB rays are generally responsible for sunburns.  Think of UVB as the BURNING (sunburn-causing) rays.

This is a very short and sweet summary to get the main points out, but you can check out this article for a more in-depth explanation.

Is higher SPF better?

Not, not necessarily. First, remember that “SPF” is only a rating on effectiveness of UVB rays, not UVA.   SPF 15 blocks roughly 93% of all UVB, while SPF 30 blocks 97%, and SPF 50 blocks 98%. (See If you are out and about, many organizations recommend reapplying sunscreen every two hours (especially if you’re spending the day in the sun). It is also more important to look for a broad spectrum sunscreen than one merely with a high SPF rating.

The way SPF works is if it takes you 10 minutes to start burning normally, wearing SPF 15 would mean it would take 15 times as long to burn–150 minutes.

How much SPF do I need? Do I need to reapply my sunscreen throughout the day?

Most recommendations seem to indicate a a full shotglass’ amount for your entire body applied thirty minutes before sun exposure and reapplied every two hours. If you’re in the water or sweating, it is even more important to reapply regularly. Even water-resistant sunscreens (designed for 40 minutes of protection in the water) and waterproof sunscreens (designed for 80 minutes of protection in the water) need to be reapplied after a romp in the water. (See

How do I reapply sunscreen over makeup?

According to WebMD, it is much better to choose a moisturizer or lotion/cream based SPF product rather than a foundation or powder with SPF in it–you may not get enough coverage if it’s within a foundation (particularly a powder) or cosmetic product.   Bauman (an expert in the aforementioned article), recommends reapplying sunscreen once during the day for day-to-day wear. To reapply sunscreen over an already-done face, consider a sunscreen spray (but made for the face, not the body), patting a layer of sunscreen or SPF-based tinted moisturizer onto the face (don’t rub), and/or pressed powder (with a sponge for better adhesion) with SPF.

In general, the ingredients in sunscreen degrade when in direct UV contact, so if you’re sitting in an office building all day, it may not be necessary to reapply.  Always remember to apply sunscreen liberally–don’t hold back–and be thorough about it.  If cost is a worry, look for a more affordable sunscreen rather than a $300/jar sunscreen!

What ingredients should I look for?

Any sunscreen or sunblock should list what ingredient(s) it uses to accomplish sun protection. The rule of thumb is to look for a sunscreen with “broad-spectrum” protection. This means that it uses ingredients that cover the majority of the UV spectrum (so both UVA and UVB protection).

  • UVB (290-320nm): Aminobenzoic Acid (PABA), Cinoxate, Dioxybenzone, Ensulizole, Homosalate, Octocrylene, Octinoxate, Octisalate (Octyl Salicylate), Oxybenzone, Padimate O, Sulisobenzone, Trolamine Salicylate, Titanium Dioxide, Zinc Oxide
  • UVA (320-340nm): Dioxybenzone, Ecamsule (Mexoryl), Helioplex, Meradimate, Oxybenzone, Sulisobenzone, Titanium Dioxide, Zinc Oxide
  • UVA (340-400nm): Avobenzone, Zinc Oxide

Physical blockers like Titanium Dioxide and Zinc Oxide may give some deeper skin tones a white cast (as they are, literally, physically blocking the rays). Some may be allergic or sensitive to chemical sunscreens and may need to opt for physical blockers instead. Physical blockers protect skin by deflecting or blocking harsh UV rays, while chemical blockers/sunscreens usually absorb them. (Most other sunscreen ingredients beyond titanium dioxide and zinc oxide are chemical sunscreens, for reference.) Physical blockers tend to be more stable, while chemical sunscreens may degrade and are often paired with other sunscreen ingredients to increase stability. (See more information at

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46 thoughts on “Sunscreen 101: UVA vs. UVB, What SPF Means, Sunscreen & Makeup

  1. Rosie

    Yay, I bought Neutrogena’s Age Shield Face with helioplex just this week and it covers the burning and aging, hopefully, haha! Now I need to find a spray for the face.

    These posts are great, I’m very excited to learn more.

    • Yes, Neutrogena is supposed to be pretty good (because of the Helioplex!) :) I know I used Neutrogena’s Dry Touch when I was in Hawaii a year or two ago!

  2. GeenaK

    Unfortunately, the website you have referenced has mixed up SPF and UPF – it’s UPF (the rating used for sun protective fabrics), that tells you what percentage of UV gets through.

    …As a dematologist once said to me “The three rules for great skin are 1. Stay out of the sun. 2. Stay out of the sun. 3. Stay out of the sun.”

  3. michelle

    i really like this series

    keep em comming

    • Mirna

      I second that! Face spray is on my beauty shopping list now! The only thing is… I have oily skin and some of these sunscreens make it worse :(
      Do you have any recommendations Christine?
      Thank you.

      • Look specifically for sunscreens marketed with a matte finish — I like Neutrogena’s Dry Touch formula, because it does dry down pretty matte and not greasy at all. Lotions are also lighter than creams!

  4. christinek

    this was great! thank you!

    one question: does the efficacy of suncreen (with both chemical and physical UVA/B blockers) change depending on whether I apply it before of after a make-up primer?

  5. DallasBrownEyes

    Thanks for the information! I am on the hunt for a pressed powder with SPF so that I can touch up during the day.

  6. Learning is awesome! I love this stuff :) Great job Christine. I love that you’re doing this series of posts – This was a great one!

    • Thanks, Dusty!

      This one was way too heard to write, LOL! I was reading studies and FAQs for hours and hours yesterday to do everything I could to make sure it was right!

  7. Dini

    Wow. Thanks for the quick and simple suncreen info session. I have darker skin and I’m always such a slacker with sunscreen (for my face especially). This was a great reminder for me to slap some on, especially with the sunny and warmer days to come. Much appreciated!

  8. Are there any particular sunscreens that you recommend Christine?

    • I love Shiseido’s for super SPF protection. I typically go Shiseido or Dermalogica if I’m out all day. Oh! and Neutrogena Dry Touch…

  9. Christine

    Great post! I finally realized that I’m allergic to chemical sunscreen a few years ago. Now I know to stick to physical blockers in both sunscreen and makeup.

    • Lee

      How did you realise you had an allergy.

      I have a matte oil free suncreen I use (chemical based) whenever I use it I get large terrible cystic acne.
      When I use non oil free sunscreen with physical blockers, I only get really small “normal” pimples.

      • Christine

        Well, it was confusing because the allergic reaction from chemical sunscreen was just like a sunburn so at first I thought sunscreen just didn’t work for me. Then I thought I was allergic to all sunscreen. I finally decided to google “sunscreen for sensitive skin” and tried physical blockers.
        I’m not sure if you have an allergy too. You might or maybe you’re just sensitive to chemical sunscreen in the sense that it clogs your pores.

  10. Chai

    Thanks for the 411!

  11. Thank you for getting this information out there! So many people don’t know enough about sunscreen!

    The amount of sunscreen you have to use to get the rated protection is 2mg/cm^2 which is where the 1/4 teaspoon for your face and shot glass for your body estimates come from. So in this sense, it is better to have higher SPF because very few people use the necessary amount to achieve the rated protection.

    And let’s not forget chemical sunscreens degrade over time and expire too!

  12. Liz V.

    Coppertone Nutrashield Faces Dual Defense SPF 70+
    This is great stuff. I love it for my face not too greasy and doesn’t sting. I really like it thought, I would share :)

  13. Kim L

    I know it is usual to use the highest sunscreen possible, but it should also be realized that this increases the amount of active ingredient and therefore the likelihood of allergic reaction increases. At a certain point the difference in SPF does not make much of a difference.
    Example SPF 25 = 96% protection, but SPF 50 only 98% and SPF 100 would only be 99%.

    Also, depending on the journal articles you read, you can find UVB to also be linked to skin cancer as well as immune suppression.

    UVA has the lowest energy and penetrates the deepest into the skin. It is linked to premature aging such as loss of collagen, change in connective tissue, and decrease in the number of blood vessels.

    When last I knew there was no rating for UVA. Do you know if that has changed?

    • It also depends on the ingredient – if you are more sensitive to ingredients, a physical blocker is better than the chemical ones!

      I believe PA (PA+++ for example ) is one measure for UVA, but I think that’s for Japan and not for everywhere at this time.

  14. Candi

    Thanks so much for this post Christine, this is my favorite post about sunscreen of all time cuz it’s concise and has all the information I’ve been wanting to know all in one place!! So now I have a question about the Shiseido Extra Smooth Sun Protection Cream SPF 38 PA+++ (which has zinc oxide) and the Ultimate Sun Protection Lotion SPF 60 PA+++ (which has titanium dioxide) according to Sephora. Does this mean if I want a broader spectrum, I should get the SPF 38 one?

    • Hey Candi,

      They both seem like they should be broad spectrum SPF. PA+++ is a rating system in place for UVA (but it’s not a U.S. based rating system).

      If you’re looking for a Shiseido face SPF, though, this one is good – Shiseido Sun Protection Cream for Face SPF 55 PA+++

      It has zinc oxide AND titanium oxide :)

      • Sarah

        I love the Shiseido Sun Protection Cream and Sun Protection Lotion. They smell great and work well under makeup in keeping me matte! I have both in SPF 55. They replaced the SPF 55 lotion with the SPF 60, but you can find the 55 for $20 at T.J. Maxx, which is where I bought both. The lotion blends more easily, but I don’t think the cream is that thick at all and blends easily as well. Check out your local T.J. Maxx to see if they have any before shelling out $14 more at Sephora/department stores.

  15. Jessi

    Clarins UV Plus SPF 40 Day Screen is the best I’ve ever tried for the face. It absorbs and coats instantly with a perfectly light, zero-grease barrier. ‘Only thing I’ve ever tried that doesn’t irritate my skin, make me break out or dry out my already dry, sensitive face. Not cheap, but it’s actually a product where a little does go a long way.

  16. Quennie

    I use the Peter Thomas Roth sunscreen in translucent powder form. I reapply it every 3 hours. It is available in Sephora and Ulta.

    • Quennie

      Of course, I only use this for reapplication. I always use a moisturizer with SPF and sometimes the Revlon Photoready Foundation (also with SPF).

  17. Diana B

    Thanks for this information Christine

  18. Luisafer

    This a great article!!!! I always wear my sunscreen!!! before just face, but this days everywhere… haven’t sun tan in years!!! too dangerous!!! besides, when you’re at the beach or pool I think I get a pretty color even though I don’t sun tan and wear sunscreen =O)

  19. Andrea

    Christine, sorry to be a pain, but I just want to be clear on this and it’s impossible to get impartial skincare advice in any shops!

    If I apply something like the SPF 50 MAC primer in the morning, then put all my make up over, spend most of the day in the office, just a short walk to work and back, a little wander at lunch time, would I be okay if I don’t top it up? I have fair skin and, even though I don’t burn, I do worry about ageing!

    • Hey Andrea,

      From what I’ve read, it sounds like that’s probably okay, unless you’re in a lot of direct sunlight in your office! That’s what Renee Rouleau (one of my favorite skincare experts) said on her blog about sunscreen, and hell, she sells sunscreen!

  20. LaDiDa

    I was wondering if anyone had any recommendations then for a sunscreen spray (made for the face)… hopefully something that works well with oily skin.

  21. Tiffany

    Hi, my mum purchases the MAC face primer SPF 50 for her holiday.
    I was wondering, if she uses that on her face and then another sunblock on her body that has a considerably lower SPF, will she get an even tan? Or will her face be pale and the rest of her body much darker xx

  22. flightperfect

    I have tried many dif sunscreens because I have oily sensitive skin, and at the end of the summer I always became a terrible cystic acne. Now I’m very happy with “50+ ANTHELIOS XL” from “La Roche Posay”. It’s for Sun Intolerant Skin Combination to oily skin, Paraben-Free.