Do I really need to reapply my sunscreen?

By now, we’ve already established that it’s important to use sunscreen or at least a moisturizer containing SPF on a daily basis. However, another question that begs asking is, do we need to reapply every two to three hours as often instructed? In the past, I was under the impression that we have to reapply. However, I now understand that this depends on the type of sunscreen you apply, as well as your lifestyle.

Chemical sunscreen
If you’re using a chemical sunscreen that contains active ingredients like Octinoxate, Avobenzone, Oxybenzone, Octoctrylene or Mexoryl just to name a few, then it is necessary to reapply as they absorb the sun’s light energy and convert it safely into thermal energy on top of the skin, which is then released. In simple terms, chemical filters intercept that radiation and transform it into something much less dangerous. The problem is this photochemical reaction uses up sunscreen according to Dr Ellen Marmur in her book Simple Skin Beauty.

Imagine that each chemical sunscreen molecule gets zapped and disappears the second it gets hit by a photon and converts to heat. Rather than wearing off, it is actually used up, like gasoline used by a car or food consumed by your body. That’s why it must be reapplied. The more sun you are getting, the faster sunscreen is used up or breaks down.

Reapply often when you’re out in the hot sun for long periods
So if you’re using a chemical sunscreen and spend a lot of time under the sun, then it’s important to reapply as often as every two hours even though some chemical filters like Mexoryl are said to be active for as long as eight to ten hours. I use such a chemical sunscreen when I head to the beach or pool and I reapply like *ahem* every half an hour. If it’s just a oouple of minutes of casual sun exposure, or if your chemical sunscreen comes with a physical sun blocker ingredient like Zinc Oxide or Titanium Dioxide, then it may not be necessary to reapply especially if you aren’t able to. But your best bet, to ensure that your sunscreen does not get used up quickly on a daily basis, is to use added protection gear like a brolly, a hat or a pair of sunglasses (or all of these).

Physical sunblock
On the other hand, if you use a mineral sunscreen or physical sunblock as they’re known containing either Zinc Oxide, Titanium Dioxide or both, then you don’t have to reapply as these physical blockers sit on the skin and provides a shield against the UV rays – unless you do not apply enough or you wipe them off due to perspiration. That also means that if you use a sunscreen containing Zinc Oxide and/or Titanium Dioxide only, then you definitely have to reapply when you go swimming.

My recommended type of sunscreen for outdoor usage
But do note that in terms of protection level, a chemical sunscreen combining chemical filters like Mexoryl with physical blockers like Zinc Oxide or Titanium Dioxide offers a higher level of protection – like those from the European brands such as La Roche-Posay that state their PPD ratings. So I would highly recommend using those if your skin is predisposed to pigmentation and you have to be exposed to the oppressive heat for longer periods. In another post, I’ll discuss how to up the ante of sun protection from within our body.


  1. Paris B says:

    Thanks for the tips. Problem with having to reapply is when you use makeup. Its impractical hence I don’t. Bad I know ?

  2. sesame says:

    It’s true…highly impractical when you use makeup.
    But if you’re not out in the sun – just walking to your car or going out for lunch, it should be okay. Used added gears like brolly and sunnies for the added protection.

  3. Zyra says:

    when you reapply, do you wait like 15-20 minutes before re-exposing yourself to the sun? that’s my problem…. because im scared that when i reapply, and i don’t have time to wait for it to absorb before sun exposure, that it would do more damage than good?

  4. sesame says:

    For chemical sunscreens, it’ll be effective between 20 and 30 mins after application. But check your ingredients, if it has one of the physical blockers, then it will provide some protection immediately because of the shielding.

  5. Amarise says:

    I have found that if you wear makeup and already use a foundation that has some SPF in it, reapplying throughout the day helps with some protection and keeping your makeup looking fresh.

    And if you wear liquid foundation, I know that there are pure zinc oxide powders that go on translucent. This is due to it having micronized particles, not nano, if you’re okay with that.

    I wear a physical sunscreen under my makeup, which is the basis of my protection for the first few hours of my day depending on what I’m doing.

  6. Grace says:

    Hi Sesame, how about blotting throughout the day? Does that remove sunblock? I use a sunblock containing both physical and chemical blockers and have oily skin, so I blot about 2 hours after first applying my make-up. My skin is matte when I’m done with my make-up but I oil up pretty fast. Am I actually blotting off the sunblock?

  7. sesame says:

    Yes, reapplying foundation will help if once wears makeup. I used to have a habit of reapplying until I started with mineral foundation and stopped doing so.

    Tried the zinc oxide powder but found it gave me an ashy look though…

  8. Chris says:

    This is a wonderful blog entry, when you consider what happens down the road without SPF, it can be quite frightening!

  9. Angel says:

    That is a relief, I do not spend much time in the sun at all. And I use a s/s that has both chem and zinc ingredients in it. ? I hate reapplying because I’d have to do my MU all over again. If I was at the beach or something, I would reapply of course, but for everyday limited exposure, I don’t bother unless I feel like I need to. I also wear sunglasses and a widebrimmed hat. And gloves when I am driving xD And in the summer, carry my little cream parasol <3

  10. sesame says:

    I assume you’re not based in Singapore from your comments about wearing gloves when you’re driving.

  11. Joyce says:

    hmm i don’t get the not wearing gloves comment. i try to wear mine out when i go out for lunch (bought a few pairs in tokyo last summer), and i’m always with my parasol and sunglasses as well

  12. CT says:

    I recently took up dragon boat but I hate getting tan. Despite me using sunblock I still get dark. Will oral sunblock helps? Save me!

  13. sesame says:

    Haha…what I meant is I think you’re not based in Singapore cos the weather here is horrible as in it’s hot and humid and it’s impossible to put on gloves when we’re outdoors. So I assume you must be from another country where the weather is more cooling.

  14. min luo says:

    Hi Sesame,
    Could you please give me some recommandations about sunscreen or moisturizer with spf for my 3-year-old daughter so she can wear it daily? If the sunscreen is water-proof or water-resistant, then how to wash it off thoroughly without hurting her face? Thanks a lot!

  15. sesame says:

    Try Jason Natural Cosmetics Earth’s Best Organic Sunblock, Chemical Free SPF 30+. I used this for my boy when he was younger and it was not bad. No burning. Not exactly water resistance so I had to reapply whenever he went swimming. But it is easy to wash off with just normal soap.

    However, I’m not so certain if you want to use this every day. Most natural sunscreens for babies do leave a whitecast, which also means the ingredients are not micronized and hence, safer.

    The current one I use on him is not so white but that’s because they use chemical sunscreen ingredients. It’s the Baby Blanklet Sunscreen and you can read my review here:

  16. min luo says:

    Thanks a lot for your time, Sesame!Actually I want to let my daughter wear sunscreen or moisturizer with spf daily on her face. But I think it’s hard to wash her face with soap everyday since she screams a lot when water gets into her eyes and nose. So is it possible to find something not water-resistant so it will be easier to wash off?

  17. sesame says:

    Okay, I suddenly remember this product I tested recently. It’s for adults but the moisturizer with SPF is very nice and you don’t need special cleansers. I checked the website and they have kid’s stuff. Have not tried but going by the adult version, think should be okay. Suggest you write to them and ask about your concerns and if the product is suitable for your daughter.

    The store is based in Singapore.

  18. min luo says:

    Thanks again, Sesame! I will definitely check the website. Your information is very helpful. I really love to read your email every night!

  19. sesame says:

    You’re welcome. ? I hope you’ll find something for your daughter.

  20. Siew Ying says:

    You mentioned that moisturisers with sunscreen (SPF) does not need special cleansers (I take it that it can be removed by soap or facial cleanser). Does that apply to all moisturisers with SPF? I really dislike putting on sunscreen (even though it’s bad) because I find it a hassle. A facialist has ever mentioned to me about Artistry moisturiser with SPF doesn’t require a makeup remover. If so, I’d be glad to use these moisturisers daily. I have been pondering over this question for quite some time, since the general conception is that any SPF product will need to be removed with a makeup remover, if used on the face.

    For now, I try my best to keep out of the sun’s way.

  21. momtomomhealth says:

    I have found Badger to be a wonderful sunscreen with Organic ingredients which will in allow you to feel a sigh of relief that the product is not going to harm your child. As Sesame stated the whitecast is a safer choice and Badger WILL leave your child with a whitecast….but I’d rather have that than the alternative which is the nano particles companies are now using to eliminate the whitecast appearance. I have also heard that you do not need to invest in SPF’s higher than 30, they can’t find relevance to justify this. Enjoy the Sun!!!

  22. maica says:

    Hi, would you happen to know where in Sg I could buy Jason Natural Cosmetics Earth’s Best Organic Sunblock? I’ve had a transplant, and my meds makes me immunosuppressed, making me high risk for cancer (esp. skin cancer). I’ve been looking up the safest sunblock. Apparently I looked up the one I’m using and it ranked 7 in hazard pts.!
    I’ve been using this site to see which products are safe for me:

    any help would be great! my email’s

    Thanks Sesame!

Leave a Reply