Sunscreen

Many beauty products today contain sunscreen. Most BB creams and foundations come labelled with an SPF factor and PA grade. The ones which Dearie recently bought for me are no exception!

Some of my skincare products which contain sunscreen

And I’d say he bought them for me just in time! Because, is that an age spot developing on my left cheek??! Why?? I’m not even 30 yet! T_T

Age spot? T_T

I remember learning about sunscreens back when I was still an undergraduate student, but I couldn’t recall much of it anymore… Time to hit the books (or rather, internet) again! To my pleasant surprise, this exercise not only refreshed my memory but I discovered new information along the way. So, let me share with you what I’ve learnt. These information apply to sunscreen in general, not just in facial products.

Sunscreen is not a stand-alone protective measure against UV radiation. Remember to also use other sun-protection measures:

·       Avoid the sun at its hottest, i.e. between 10am to 4pm.

·       Wear protective clothing, i.e. long pants, long sleeves, sunglasses, and an umbrella or a wide-brimmed hat.

What is the difference between SPF and PA grade?

Firstly, a short introduction to UV radiation:

There are 2 types of UV rays that reach the earth’s surface: UVA (wavelength 320-400 nm) and UVB (wavelength 290-320 nm). UVB causes skin redness, inflammation and stinging – effects we can easily identify as sunburn. UVA penetrates into the deeper layers of the skin and may have greater destructive effects.

SPF = Sun Protection Factor. SPF mainly measures UVB protection.

Note: I used to think that SPF number corresponds to the length of time you can be exposed to sunlight without burning, e.g. if I would normally get a sunburn after 10 mins, an SPF 30 sunscreen would allow me to stay out 30 times longer (300 mins) before getting a sunburn. But, to my surprise, I found that this is not exactly accurate. Another piece of info: the relationship between SPF and UVB protection is not linear - a sunscreen with SPF 15 can filter 94% of UVB radiation, whereas SPF 30 provides >97% protection.

But let’s not get caught up with the details. The most important factor contributing to the efficacy of sunscreen is not really the SPF number, but whether or not we use it correctly – which I will talk about later below.

PA = Protection grade of UVA. This is the Japanese measurement of sun protection, and is not recognized by the FDA. The rating system ranges from + (lowest protection) to +++ (greatest protection).

Besides PA grade (commonly used in Asian products), product labels in other countries use different ways to indicate UVA protection. In the US, the FDA requires delineating “broad-spectrum” and sun protection factor (SPF) information on the label of sunscreens which protect against both UVA and UVB. In the European Union, the UVA logo is used.

FDA requirement for "broad spectrum" to be displayed on label

EU UVA logo

When you choose a sunblock, make sure to select one that confers both UVA and UVB protection!

What is the active ingredient in sunscreen?

There are 2 main types of active ingredients:

·       Physical sunscreens – these are particles such as zinc oxide and titanium oxide which physically reflect UV radiation. Very similar to wearing clothes to block the sunlight! The downside, though, is that the texture of these products can be pasty and clumpy. They may also leave a white residue on the skin. However, with advances in nanotechnology, these particles can now be processed to be really, really small so that they no longer cause these problems.

·       Chemical sunscreens – these are organic compounds which absorb UV radiation. Different active ingredients absorb UV radiation at different wavelengths, so it is not uncommon to see several active ingredients blended together in the same product in order to achieve broad-spectrum coverage.

What is the correct way to use sunscreen?

·       Apply a generous amount of sunscreen to dry skin 30 minutes before sun exposure.

·       Apply sunscreen to all skin surfaces that will be exposed to sun, e.g. face, ears, hands, arms and lips. If you don't have much hair on your head, apply sunscreen to the top of your head or wear a hat.

·       Reapply sunscreen every 2 hours, and immediately after swimming or heavy sweating.

·       Be aware that sand, water, snow and concrete reflect sunlight, making it all the more important to use sunscreen.

·       UV light can pass through clouds, so use sunscreen even when it's cloudy.

What is the incorrect way to use sunscreen?

The use of sunscreen to enhance tanning and deliberately prolong exposure to the sun is an abuse of the product and may actually increase the risk of skin cancer. A common misperception is that sunscreens decrease the risk of sunburns and therefore, it’s OK to stay out in the sun for a long time. But this could increase the risk of skin cancers and cause photoaging (e.g. wrinkles, sunspots).

What can sunscreen protect me against?

·       Sunburn (Yep, that’s a no-brainer.)

·       Immunosuppression. Yes, that’s right. UV radiation can suppress our immune system, and this can contribute to the development of skin cancers. Quite scary, huh? Thankfully, research shows that broad-spectrum sunscreens do protect against immunosuppression.

·       Skin damage such as solar elastosis (thickened, dry, wrinkled skin) and decreased skin elasticity. Interestingly, sunscreens are still beneficial even at lower levels of UV exposure which do not cause sunburn.

·       Some types of skin cancers. Sunscreens can help prevent the formation of squamous cell carcinoma and actinic keratosis (thick, scaly patches of skin which can potentially progress to squamous cell carcinoma). However, there is no strong evidence that they also prevent other types of skin cancers such as basal cell carcinoma and melanoma.

Are there any harmful side-effects of sunscreen?

·       Although rare, there are people who develop allergies to some chemical sunscreens.

·       Some chemical sunscreens may be absorbed through the skin into the bloodstream. (This is less of a concern with non-soluble sunscreens such as zinc oxide & titanium oxide.) Could it potentially cause harm in the body? Some animal studies suggest that selected sunscreens may alter hormone levels. However, such effects have not been shown in humans.

·       Are nanoparticles of zinc oxide and titanium oxide small enough to be absorbed by the skin? Worry not, many studies have shown that they do not penetrate the skin.

If sunscreens may cause harm, should I still use them?

UV radiation has long been known to cause skin damage and even cancers. These harmful effects can be prevented by taking sun-protective measures including staying out of the sun, wearing protective clothing and using sunscreen. There may be some concerns about product safety of sunscreens, but it is definitely reassuring to know that each active ingredient has to pass a very stringent safety evaluation before their approval in the EU, US and Japan. With the very favourable risk-benefit profile of sunscreens, I would definitely recommend their use.

Of course, if you develop an allergic reaction, stop using the product immediately. See a doctor, especially if the allergic reaction is severe.

If I were pregnant or breastfeeding, I might choose to be kiasi (Singlish for “afraid to die”) and use physical sunscreens instead of chemical ones - just for the peace of mind that the sunscreen will not be absorbed into my body and passed to the baby.

References:

1.       Mayoclinic

2.       Jou PC, Feldman RJ, Tomecki KJ. Cleve Clin J Med. 2012 Jun;79(6):427-36

3.       Krause et al., Int J Androl. 2012 Jun;35(3):424-36

4.       Lodén et al., Br J Dermatol. 2011 Aug;165(2):255-62.