Skincare 101: Sun Damage and SPF

There’s a topic that I’ve always wanted to post but has been putting off for a year now due to amount of research required — sun protection. This will hopefully be a comprehensive but quick reference to sun damage, SPF and different ways to protect yourself.

Sun Damage: How and Why?

You need sun protection all year round, all the time. Sun damage comes from UV radiation, not just light and heat, so you still need to be protected in the winter and on cloudy days. And UV radiation is especially strong in high altitude or around reflective surface (snow). However, do try to avoid going outside 10am – 3pm, which is when the sun is strongest.

You need protection against both UVA and UVB. UVC have the shortest wavelength and is completely filtered by the atmosphere so don’t worry about it. UVB affect the surface of the skin, it is the main cause of sunburn and skin cancer. UVA acccounts for 95% of the UV rays that reaches the earth and is able to penetrate deep below the skin. It is the main cause of tanning and aging/wrinkling. While UVB doesn’t penetrate glass, UVA do, so you need sun protection even if you are behind a window.

Sun damage on the scalp? yes it can happen. Do you know it’s possible to get sun damage and skin cancer on your scalp? It’s more difficult due to hair, but if you are outside for long under intense UV rays, wear a hat or use a SPF formulated for scalp/hair.

Don’t tan, period. A tan results from injury to the skin’s DNA; the skin darkens in an imperfect attempt to prevent further DNA damage. These imperfections can lead to skin cancer. The sunlamps used in tanning salons emit doses of UVA as much as 12 times that of the sun. People who use tanning salons are 1.5-2.5 times more likely to develop cell carcinoma. You WILL get sun damage even if you have a tan or darker skin color.

Sun damage can take decades to show, it’s never too late or early to protect yourself. Sun damage (wrinkles and pigmentation) can take 10-20 years before they become apparent. Most people neglect sun protection as kids then start to see signs in their 20s. Just because you don’t see it (yet) doesn’t mean the damage is not there.

How to Pick Your Sunscreen?

SPF do not cause cancer. There was the scare awhile back about SPF causing cancer, details here, here and here. Long story short:a few studies done on rodent seems to show a correlation between sunscreen and skin cancer, but they did not see such results on human. They did mention that people using sunscreen may have been more negligent due to feeling of safety, and the type of sunscreen was not taken into consideration. A few studies also  mention oxybenzone is a hormone disruptor and may cause cancer, but there are many many more studies (that are more scientifically rigorous) that disproves it.

Ultimately what it comes down to is to choose the correct sunscreen and using it correctly. Up until a few years ago, sunscreen was not regulated by FDA so companies can put whatever they want on the label. But now the requirements are more strict due to FDA, so there’s no misleading labels anymore, use the right ones and you will be fine.

Use SPF30 daily, higher if you are outdoor a lot. Sun Protection Factor is a measure of time it takes for UV rays to penetrate skin. SPF 15 blocks about 94% of UVB rays; SPF 30 blocks 97%; and SPF 45 blocks about 98%. Nothing blocks 100% of UV rays, which is why labels of SPF70 and SPF100+ were misleading and no longer allowed. Now with FDA regulation, products can’t be labeled higher than SPF50. SPF30 for daily use.

Choose full spectrum or broad-spectrum. You need to be protected against UVA AND UVB, so make sure the description of the sunscreen you are using mentions both, or is labeled full spectrum/broad spectrum.

Apply SPF correctly and frequently. Most sunscreen needs to reapplied every 2-3 hrs. Because some sunscreens are only effective after they are absorbed, it’s best to apply 15-20 minutes before going outside. As for how much, the general rule is a shot glass for your whole body and a nickel-sized dollop for your face (which is why you shouldn’t solely rely on SPF in makeup, unless you really wears that much makeup). Mixing sunscreen with another product dilutes the SPF, so layer them instead. Also, don’t forget top of your ears, eye area, lips and neck/decollete if you wear low cuts. Lastly, there’s no such thing as “waterproof” sunscreen, another false advertising FDA got rid of. There is “Water-resistant”, which means that it stays effective in water for the time indicated.

Don’t forget storage and expiration dates. Most SPF are good for 3 years, but you don’t know how long it has sat on the shelf, so replace every 2 years to be safe. Some thinner sunscreen needs to be shaken before using but if color, scent or texture changes, ditch it! Also, high temperatures can cause the sunscreen’s active ingredients to degrade faster and become less stable, so don’t store it in temperature above 77 degrees Fahrenheit.

Physical vs. chemical sunscreen. Physical or mineral sunscreen are made of inorganic particles such as zinc oxide or titanium dioxide. They work as a barrier and physically blocks/deflects UV rays, which is why they tend to be thick and leave a white residue. Chemical sunscreen are made of organic ingredients such as avobenzone. They absorb UV rays and release the energy as heat, which is why they blend and look nicer on the skin. Because chemical sunscreen absorbs, physical sunscreens are generally recommended for people with sensitive skin. Most sunscreen consists of a mixture of both, which seems to be most effective. But because of that, don’t assume you are allergic to all sunscreen when you might only be allergic to a specific ingredient. For more info and a handy list of most popular physical and chemical sunscreen ingredients, click here.

DIY sunscreen? Don’t do it unless you have to. But if you do find yourself allergic or getting breakouts from all sunscreens, then it might be good to add these oil into your skincare, because any protection is better than none at all. I do not recommend using these as substitute for SPF since the degree of protection varies and they oxidize easily. If you want to boost the power of your SPF tho, antioxidants are great supplements.

Does it interfere with absorption of vitamin D? The difference in amount of vitamin D absorbed when wearing SPF and when not wearing it is not significant and you do still get vitamin D even if you wear SPF. You will have to stay in the sun until the skin tans and burns to get all the vitamin D you need in a day, so getting it from food is a much better choice. Foods that have high levels of vitamin D include fish oil, salmon and sardines, soy milk, eggs, fortified dairy products and mushrooms. Also, make sure you are actually deficient before start taking supplements since too much vitamin D can be detrimental.


If you are worried reapplication will ruin your makeup, there are plenty of colorless SPF powder and sprays that you can apply on top of it (just don’t breath them in) so there’s no excuse to not reapply. Say no to sun damage, and cheers to a year of good skin!

My reference, if you are interested in reading more:


7 thoughts on “Skincare 101: Sun Damage and SPF

  1. I loved this post! Answers to a lot of thorny questions about SPF! Kudos for doing all the research for us lazy folks! 🙂

    1. Glad it helps! Lol, I’ve been wanting to do it since last year, but it’s such a big topic and I’ve got so many questions. Figures I’d tackle it during break, it’s hard not to write a 5 page essay about it with all the information available out there. =D

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