The Sunscreen Project, Part 13: Articles (Updated)

/ Saturday, November 10, 2012 /
In this part of the Sunscreen Project, there will be an intermission my reviews. This post will focus more on the different scientific aspects of sunscreen, its properties, risks, advantages, etc.

Note: This article will take more of a scientific purpose. I will try my best to define any terms that are "super scientificky" or are delved deep jargon of medical language. If you are confused by any of the terminology or have any questions about anything I've written (or would like to dispute me/have any comments/concerns/etc over the facts) please feel free to comment. All constructive comments/questions/criticisms/etc are welcome!

I have cross-referenced my comments with many sources, ranging from articles I've read from other professionals and/or skincare specialists/aficionados. I will not link any primary literature in my sources (primary literature = scientific articles), because (1) if I did this post would be twice as long, (2) not everyone has PubMed access to the articles listed, due to subscription issues, and (3) many of the articles I will cite already have primary literature citations.

Disclaimer: As the time of this published post, I am a first-year medical student. I am in no way a licensed medical professional. Please take my writings with an educational intent. This is in no way a replacement for consultations from licensed medical professionals. Please note that, should you decide to follow my advice, you bear full responsibility for your decisions.


Okay. Enough of that jargon and legal disclaimer. Let's get down to the gist of it. Note: I am not going to be writing a super lengthy article about exactly how the mechanisms of things work during sunscreen; I will just be summarizing facts. I have linked articles at the bottom of this page about sunscreen/sunblock/etc and how it helps.

I first really got down into the facts of sunscreen from articles about SPF.

Facts about sunscreen in general:
  • There are actually 3 main types of sun rays: UVA, UVB, and UVC.
  • UVC rays are mostly shielded by the Earth's ozone layer.
  • The SPF factor measures a form of protection of UVB rays only. UVA ray protection measurements are in other systems, such as the Japanese PA+ rating system
  • UVA rays cause long-term aging damage, UVB causes tanning/burning
  • Must be reapplied every 40 or 80 min (according to FDA guidelines) - wears off eventually
  • Recent FDA regulation changes: no SPF factor can be above 50, sunscreen cannot be labeled as "waterproof" or "sweatproof", and must be listed as providing 40 or 80 min of protection
  • Sunscreen is the EXACT SAME THING as "moisturizer with SPF". Sunscreens/sunblocks are extremely emollient, and are notorious for being very greasy. 
  • For "non-comedogenic" labels: non-comedogenic means not causing acne/breakouts. However, depending on the size of each person's pores, it is different. Thus, what may be non-comedogenic for one person may cause another person to break out completely.
Facts specifically about SPF:
  • SPF measures protection against UVB rays
  • Measures percentage of UV rays protected against
  • SPF 15: 93%, SPF 30: 97%; if SPF > 30, then remains in 97-98% range
  • Above SPF 30 (or even 50), increased protection is minimal.
  • Recently, FDA changed regulations for writing about sunscreen SPF labels: maximum value that can be posted is SPF 50.
  • FDA recommends people to use sunscreen with ratings of 30 or more.
  • What matters more than SPF rating is the AMOUNT of sunscreen that is used. General rule of thumb: a tablespoon amount should be used for the head/neck, and a shotglass full should be used for entire body, from head to toe.
Sunscreen vs sunblock:
  • Sunscreens: protect by absorbing and filtering UV rays after penetrating the skin (whether UVA, UVB, or both)
  • Sunblocks: protect by reflecting both types of rays, so no penetration occurs
  • Sunscreen: uses chemical method to absorb/filter. Chemicals include avobenzone (for UVA rays), oxybenzone, octisalate, homosalate, octocrylene, oxtinoxate, menthyl anthralate, oxtocrylene. As a result, is often called "chemical sunscreen
  • Sunblock: physical barrier ingredients, sit on top of the skin, including titanium dioxide and zinc oxide
  • Sunscreen: needs to be absorbed in the skin for 15-30 min before starts becoming effective
  • Sunblock: takes effect immediately upon application
Sunblock specifically:
  • Often called "physical sunscreen" because of its physical barrier properties
  • Zinc oxide provides a better spectrum of protection (wider range of protection) when combined with other ingredients than titanium oxide
  • Causes "white cast" on the skin when applied (thus chemical sunscreens have an aesthetic factor advantage as compared to sunblocks). However, companies have been getting better about this by microionizing particles (aka reducing their size to the order of magnitude of 10-100s of nanometers, aka 10^(-9) meters). Just for reference, a red blood cell (diameter = 7.5 micrometers) is about 75 times bigger than one of these particles! 

UVA rating system (PA+ rating system):
  • Use the PPD (Persistent Pigment Darkening) rating, after 2-4 hours of sun exposure
  • PA+ provides some UVA protection with a factor of PPD 2-4
  • PA++ provides moderate UVA protection with a factor of PPD 4-8
  • PA+++ provides good UVA protection with a factor of PPD > 8
  • Generally, the more the "+"s, the better it is
  • A lot of Asian and European sunblocks have this system on this rating, and display it on their bottles
USA vs Asian vs European sunscreens/sunblocks:
  • USA considers sunscreen/sunblock as a over-the-counter drug and is regulated under FDA (US Food & Drug Adminstration).
  • Europe and Asia consider sunscreen/sunblock as a cosmetic item, so it is regulated under different terms.
  • Result? There are sunscreen ingredients that have made it into European and Asian skincare products that haven't made it into USA products yet. 
  • As of July 06, 2012, (quoted from, "in the US, there are only 17 approved active sunscreen ingredients. In Europe, there are 28. In Japan, there are more than 40."
  • Example: Tinsorb - a new ingredient used in chemical sunscreens, is a chemical that is highly stable, protects against UVA and UVB rays, and does not have any long-term exposure damage, according to current studies. It has been used for several years on the European market but has just recently hit hit US stores. Another example would be CC creams.
Miscellaneous about sunscreen/sunblock:
  • Makeup with sunscreen doesn't contain the optimum amount of sunscreen protection
  • Coconut oil has inherent SPF 4 protection
  • Your lips need protection too - use a chapstick/lip balm with spf
  • Even on cloudy days, UVA/UVB rays are pushing through
  • UV rays are even emitted from computer screens, although the effects of them are minimal compared to what you're exposed to out in the sun
  • It's a really good habit to put on sunscreen/sunblock every morning - especially to incorporate it into your morning routine.
  • Search for the best sunscreen/sunblock for your skin - reviews are opinions of different people with different skin types. You can look at reviews for directions for products to try, but ultimately, what works best for your skin depends on you!

Whew! Yep, that was definitely a lot of facts. I hope this was a useful, overall comprehensive lesson on sunscreen protection. We definitely need protection from the sun - skin cancer definitely something that is good to prevent.

Articles from Futurederm:
Articles from LiveStrong:

United States Environmental Protection Agency (EPA):

Other (just for references, and to cross-reference, along to see a source that a lot of people read):


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