Fun in the Sun

I got my first sunburn this summer (ouch) because I forgot to put on sunscreen. Actually, I pretty much forgot to use sun protectant the whole summer. That got me thinking about sunscreen. It’s just something that we rub onto our bodies, so how does it protect our skin? So in this post I’m going to investigate how sunscreen works, why it’s important to protect your skin from the sun, and how to do so.

The reason we need to protect our skin is because of the UV rays that are present in sunlight. UV rays come in wavelengths from 10nm to 400nm, but there are 3 main categories: UVA (315-400nm), UVB (280-315nm), and UVC (100-280nm). UV radiation has “low penetration” so its effects are mainly limited to the skin. (Encyclopædia Britannica, 2013)

(Skin Cancer Foundation, 2013) – diagram of UV ray penetration of skin

UVC rays are completely absorbed by the Earth’s atmosphere, so we don’t need to worry about that. It’s the UVA and UVB rays that cause trouble. UVB rays are the ones responsible for sunburns and suntans. (Everyday Mysteries: Fun Science Facts from the Library of Congress, 2010) UVA rays, since they have a longer wavelength, penetrate deeper and are the main cause of wrinkles and age spots. (Bytesize Science, 2012) UVA rays can also penetrate through clouds and glass, and 99% of the UV rays that reach the Earth’s surface are UVA rays. (Encyclopædia Britannica, 2013) Both UVA and UVB rays can cause skin cancer. (US Food and Drug Administraton, 2011) Also, sun exposure is responsible for 90% of wrinkles! (Youtube, 2013)

To protect ourselves from these UV rays, sunscreens were invented. There are two types of sun protectants available: chemical and physical sunscreens. Physical sunscreens, also known as inorganic sunscreens, are made out of nanoparticles that are approximately 100nm. They act as tiny reflectors on the skin to deflect and scatter the UV rays that shine onto our skin. (PBS Newshour, 2010) The large particle size is also what attributes to the “white cast” look of sunscreen on the skin. (About.com Chemistry, n.d.) Typical ingredients in physical sunscreens are titanium dioxide and zinc oxide.

physical sunscreen

(Bytesize Science, 2012) – structures of titanium dioxide and zinc oxide

Chemical sunscreens, also known as organic sunscreens, are much smaller in size, around 40-50nm. The small sizes of the nanoparticles allow it to be more transparent than physical sunscreens. (PBS Newshour, 2010) The most common ingredients in chemical sunscreens are octinoxate and avobenzone. (Bytesize Science, 2012)

chemical sunscreen

(Bytesize Science, 2012) – skeletal structure of octinoxate and avobenzone

Unlike physical sunscreen, chemical sunscreens protect the skin by absorbing the UV rays instead of reflecting it. The molecules in the sunscreen absorb the high-energy UV photons, and the electrons become “excited.” When the molecule returns to its original state, the energy it absorbed is released as insignificant amounts of heat. This process can be done more than once, in a cycle. (Nonprescription Drug Manufacturers Association and Cosmetic, Toiletry, And Fragrance Association, 1998)

Yikes, those UV rays don’t sound nice at all. In the interest of having younger looking skin, not getting a nasty sunburn, and preventing skin cancer, protecting our skin from the sun is a must. Physical sunscreens can only defend our skin from UVB rays, but chemical sunscreens can protect our skin from both. So when buying sunscreen, look for products that are labeled “broad spectrum” or have a PA value because those indicate both UVB and UVA protection. (Youtube, 2013)

(Youngerberg, 2013) – sunblock that have UVA and UVB protection

SPF, which stands for “sun protection factor,” can be a useful way of determining the effects of sunscreen. If your skin can stand 10 minutes in the sun without burning, then a SPF of 30 will allow your skin to be out in the sun for 30×10, or 300 minutes (5 hours), before burning. (About.com Chemistry, 2010)  Keep in mind that most people don’t put on enough sunscreen (a shot glass worth, or 45mL, of sunscreen is what’s recommended to cover your body), and sweat and water can make the sunscreen less effective, so it is important to reapply sunscreen often (around every 2 hours if you’re active).

It seems that I’ve found the fountain of youth – sunscreen! The next time you’re out in the sun, remember to protect yourself from those pesky UV rays, and do yourself a favor by putting on sunscreen. You’ll thank yourself when you’re older!

References

About.com Chemistry (n.d.). How Does Sunscreen Work?. [online] Retrieved from: http://chemistry.about.com/od/howthingsworkfaqs/f/sunscreen.htm [Accessed: 19 Sep 2013].

About.com Chemistry (2010). How to Choose the Best Sunscreen. [online] Retrieved from: http://cancer.about.com/od/skincancerprevention/a/choosesunscreen.htm [Accessed: 19 Sep 2013].

About.com Pediatrics (2010). SPF – Sun Protection Factor and Sunscreen. [online] Retrieved from: http://pediatrics.about.com/od/pediatricsglossary/g/710_spf.htm [Accessed: 19 Sep 2013].

Bytesize Science (2012). Repelling the Rays: The Chemistry of Sunscreen – Bytesize Science. Available at: http://www.youtube.com/watch?v=wopwVVsbvWI [Accessed: 19 Sep 2013].

Discovery Fit and Health (n.d.). What do SPF numbers mean?. [online] Retrieved from: http://health.howstuffworks.com/skin-care/beauty/sun-care/spf.htm [Accessed: 19 Sep 2013].

Everyday Mysteries: Fun Science Facts from the Library of Congress (2010). How does sunscreen work?. [online] Retrieved from: http://www.loc.gov/rr/scitech/mysteries/sunscreen.html [Accessed: 19 Sep 2013].

Gizmodo (2013). How Sunscreen Works (And Why You’re Wrong About It). [online] Retrieved from: http://gizmodo.com/how-sunscreen-works-and-why-youre-wrong-about-it-508910004 [Accessed: 19 Sep 2013].

Live Science (2010). How Does Sunscreen Work?. [online] Retrieved from: http://www.livescience.com/32666-how-does-sunscreen-work.html [Accessed: 19 Sep 2013].

Nonprescription Drug Manufacturers Association and Cosmetic, Toiletry, And Fragrance Association (1998). Tentative Final Monograph for OTC Sunscreen. [e-book] Food and Drug Administration. Available through: www.fda.gov http://www.fda.gov/ohrms/dockets/dailys/00/Sep00/090600/c000573_10_Attachment_F.pdf [Accessed: 19 Sep 2013].

PBS Newsroom (2010). Just Ask: How Does Sunscreen Work?. [online] Retrieved from: http://www.pbs.org/newshour/rundown/2010/12/just-ask-how-does-sunscreen-work.html [Accessed: 19 Sep 2013].

Science & Engineering News (2002). C&EN: WHAT’S THAT STUFF? – SUNSCREENS. [online] Retrieved from: http://pubs.acs.org/cen/whatstuff/stuff/8025sunscreens.html [Accessed: 19 Sep 2013].

ultraviolet radiation. (2013). In Encyclopædia Britannica. Retrieved from http://school.ebonline.com/levels/high/article/74181

US Food and Drug Administration (2011). How Sunscreen Works. Available at: http://www.youtube.com/watch?v=cC-d9ZsnLds [Accessed: 19 Sep 2013].

Youtube (2013). The Ultimate Guide to Sunscreen. Available at: http://www.youtube.com/watch?v=V46vfg-7dEI [Accessed: 19 Sep 2013].

Images

Bytesize Science (2012). Repelling the Rays: The Chemistry of Sunscreen – Bytesize Science. [image online] Available at: http://youtu.be/wopwVVsbvWI?t=1m32s [Accessed: 19 Sep 2013].

Bytesize Science (2012). Repelling the Rays: The Chemistry of Sunscreen – Bytesize Science. [image online] Available at: http://youtu.be/wopwVVsbvWI?t=1m54s [Accessed: 19 Sep 2013].

Skin Cancer Foundation (2013). Untitled. [image online] Available at: http://www.skincancer.org/Media/Default/Page/prevention/uva-and-uvb/UV-Radiation-and-Skin.jpg [Accessed: 22 Sep 2013].

Youngerberg, E. (2013). Untitled. [image online] Available at: http://3.bp.blogspot.com/-yUMjMYMQdHI/T9tY7Sz0ozI/AAAAAAAAAzw/1bQlGeeBymU/s1600/photo-89.JPG [Accessed: 22 Sep 2013].


One thought on “Fun in the Sun

  1. Summer and fall are gone, and now winter is here in Shanghai. During summer, I was covered with sunscreen because I have very sensitive skin, so I get easily burned and get a rash that is so itch. I stayed in Shanghai for Winter break, and as winter came, my skin reacted to the climate directly. Was it the sun or UV light? No, this wasn’t the case for my skin. Now, my skin is dry as a deserted land with cracks on it. This would be a miniscule problem for some people, but it is significantly critical for me because it gets itchy and dry just like when I get exposed in the sun (even without a burn). For me this symptom can be solved my using humectant (hydration solution, such as lotion), but I found out that this is an actual disease if this gets serious. Noticing this phenomenon every winter I started to wonder what is it that is affecting my skin every winter, so that I would have to put extra lotion to keep my skin hydrated? This disease/symptom is called, “Xerosis Curtis” (also known as Xeroderma or Xerodermia) (Wikipedia 2014).

    Finding out that this is surely a common problem that can be seen within an elderly population, I was still left with the question about my skin. “Dry skin is common, especially in the elderly. It is usually a minor and temporary problem, but may cause discomfort”(Healthlines n.d.). I know that surely this is more “common” during winter times (Healthlines n.d.), and I thought about what are different factors affecting my skin internally and externally. I deviated from common causes for this, but I looked at other specific chemistry related causes for this symptom. Through different steps of research process of finding out causes for this problem, from researching the most basic causes like winter itching to researching more specific causes like medications that could have affected my skin to be dry.

    (http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=444795) (Pubchem n.d.).

    I found out that most medication treatment for acne could cause problems with my skin, and this drug is called, “Tretinoin” (also known as Retin-A). “Tretinoin is a derivative of vitamin A” and how it works is by “reducing number of layers of skin cells. In patients with acne, new cells replace the cells of existing pimples, and the rapid turnover of cells prevents new pimples from forming.” Apparently, this mechanism is used in wrinkle reduction and also treated for darkened skin, which is called hyperpigmentation. (Medicinesnet) Well, as I learned these facts, its relation to food chemistry of intrigued me how can a nutrient be used diversely like this. Then, I went on to researching further into vitamin A because Tretinoin is a derivative of vitamin A. I learned in food chemistry chapter that Vitamin A (retinol) is derived from carotene (chem options). Moreover, deficiency symptoms “include night blindness, excss skin dryness and a lack of mucous membrane secretions”. (Derry 2009). This is probably one of the reasons why retin –a is used for acne solution. However, that is not because retin-a’s effect is “irritating the skin and causing the cells of the skin to grow (divide) and die more rapidly, increasing the turnover of cells. The number of layers of cells in the skin actually is reduced. In patients with acne, new cells replace the cells of existing pimples, and the rapid turnover of cells prevents new pimples from forming” (Medicinesnet). This has an implication that, because retin-a derives from vitamin A, retin- a and vitamin must share similar effects such as causing skin to grow and die more rapidly, increasing the turnover of cells. Vitamin A is recently known to have an effect in cell differentiation (National Center for Biotechnology Information n.d.) and this supports implication that because retin-a derives from vitamin A, they must share similar effects.

    (http://en.wikipedia.org/wiki/Vitamin_A) (Wikipedia)

    Other than causes and effects of vitamin a and retin –a, I looked and compared chemical composition and formation of the two compounds. There is not a huge difference, but first, retinoid (retin A) is a synthetic derivative of retinol (vitamin A) derived from its retinoic acid. Retinol is formed in the body by the hydrolysis of retinyl esters. Unlike retinoid, it does not have direct effect because “it must first be converted by enzymes into retinoic acid. The conversion rate of retinol to retinoic acid is quite slow and varies among individuals”. On the other hand, retinoid is “stronger than retinol, and also has a direct effect as a skin treatment. By providing a light chemical peel”. However, one needs to pay attention to safety implications because retinol doesn’t need any prescription while retinoid does need a prescription. Retinoid is usually used in cancer treatment too because of its properties. (Livestrong n.d.)

    It was acne treatment that I took sometimes that got me a dry skin, but at the same time could have provided me vitamin A. Dry skin a.k.a xeroderma is not a fear for human these days with so many cosmetic products out there, but I recommend one with no synthetic additives because just like what I mentioned in safety considerations, one needs to take care of what skin type does he or she have and decide on what to put on one’s skin. Moreover, consuming natural product is always better than synthetic cosmetics when it’s not necessary unlike me. And I also recommend keep being hydrated and consume regular amount of vitamin A. (If you consume too much you can die from hypervitaminosis A that intoxicates you).

    References:

    Facts:

    Center for Biotechnology Information. (n.d.). Result Filters. National Center for Biotechnology Information. Retrieved January 13, 2014, from http://www.ncbi.nlm.nih.gov/pubmed/7832047

    Derry, L. (2009). Chemistry for use with the IB diploma programme options: standard and higher levels. Port Melbourne, Vic.: Pearson Australia.

    Mayoclinic. (n.d.). Dry skin. Definition. Retrieved January 13, 2014, from http://www.mayoclinic.org/diseases-conditions/dry-skin/basics/definition/con-20030009

    Wikipedia. (2014, October 1). Xeroderma. Wikipedia. Retrieved January 13, 2014, from http://en.wikipedia.org/wiki/Xeroderma

    Healthlines. (n.d.). Xerosis Cutis. Healthlines RSS News. Retrieved January 13, 2014, from http://www.healthline.com/health/xerosis

    Livestrong. (n.d.). The Difference Between Retinol and Retin-A. LIVESTRONG.COM. Retrieved January 13, 2014, from http://www.livestrong.com/article/415718-the-difference-between-retinol-and-retin-a/

    Medicinenet. (n.d.). Dry Skin (Xeroderma) Home Remedies, Causes, Treatment – MedicineNet. MedicineNet. Retrieved January 13, 2014, from http://www.medicinenet.com/dry_skin/arti

    National Library of Medicine. (n.d.). Vitamin A: MedlinePlus Medical Encyclopedia. U.S National Library of Medicine. Retrieved January 13, 2014, from http://www.nlm.nih.gov/medlineplus/ency/article/002400.htm

    National Library of Medicine. (n.d.). Vitamin A: MedlinePlus Medical Encyclopedia. U.S National Library of Medicine. Retrieved January 13, 2014, from http://www.nlm.nih.gov/medlineplus/ency/article/002400.htm

    Vitamin A. (n.d.). — Health Professional Fact Sheet. Retrieved January 13, 2014, from http://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/

    Wikipedia. (2014, October 1). Xeroderma. Wikipedia. Retrieved January 13, 2014, from http://en.wikipedia.org/wiki/Xeroderma

    Images:

    Pubchem. (n.d.). Tretinoin – PubChem. Tretinoin – PubChem. Retrieved January 13, 2014, from http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=444795

    Wikipedia. (2014, December 1). Vitamin A. Wikipedia. Retrieved January 13, 2014, from http://en.wikipedia.org/wiki/Vitamin_A

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