So there begins my search for the perfect sunscreen. Many sunscreens now offer adequate protection against UVA and UVB rays. However, many of them also contain ingredients which are unsafe. We will focus on the broad spectrum sunscreen ingredients, which is what we should be looking for. These protect us against UVA and UVB rays.
UVA/UVB Rays
Firstly, we have to understand that there are two types of damaging UV rays, UVA and UVB rays. UVA are aging UV rays which causes wrinkling, sunspots and indirectly, skin cancer. It is a deeply penetrating UV ray which damages collagen fibers, vitamin A in the skin, and produces free radicals and reactive oxygen species. UVB are burning UV rays which are the primary cause of skin cancer and sun burn. These rays cause direct DNA damage which results in mutation and in some cases, cancerous growths. UVB (burning) has a wavelength range (in nanometers) of 280-320nm. UVA (aging) has a wavelength range (in nanometers) of 320-400nm. Note that here are short (UVA-II) and long (UVA-I) UVA rays. Not all sunscreens that protect against UVA can protect against both short and long UVA rays. A good sunscreen that protects our skin against both UVA and UVB rays should be able to protect against UV rays from wavelengths 280 to 400 nm. These are called broad spectrum sunscreens.
Sunscreen Ingredients Chart from http://www.bloggang.com/mainblog.php?id=pupesosweet&month=13-11-2008&group=6&gblog=20
According to the chart above, the broad spectrum sunscreen ingredients are Titanium Dioxide, Zinc Oxide, Tinosorb S, Mexoryl XL, Mexoryl SX and Tinosorb M. These are further categorized into Physical, Chemical and Hybrid sunscreen ingredients.
Physical Protection
Physical sunscreen ingredients work by forming a layer of film on top of the skin that reflects or scatters UV light. It doesn’t get absorbed into the skin, and thus, does not cause allergic reactions. Titanium dioxide and Zinc Oxide are the most frequently used in sunscreens containing physical ingredients. However, they are easily rubbed off and are unsightly, often leaving a whitish tint.
Chemical Protection
Chemical sunscreens work by absorbing the UV rays before they damage your skin, but they are also absorbed by the skin. Some people experience allergic reactions and can cause eyes to sting when perspiring.
Hybrid Protection
Hybrid sunscreens act as both chemical and physical sunscreens. They work by absorbing UV rays and also reflecting and scattering UV rays.
Zinc Oxide 290-400 nm
Zinc Oxide protects you from UVB and both long and short UVA rays. Zinc oxide is non-irritating. In fact, it is used widely for medical purposes as a skin protectant and anti-irritant. It is currently the broadest spectrum UVA and UVB physical reflector available in the market. It is also photostable, making it a safe choice for use as a sunscreen. However, do take note of sunscreens with nanoparticles of Zinc Oxide. There are studies which show that nanoparticles can take on different properties and be potentially damaging to health.
Titanium Dioxide 290-350 nm
Titanium dioxide protects you from UVB and short UVA rays, but not long UVA rays. The titanium dioxide particles used in sunscreens have to be coated with silica or alumina, because titanium dioxide creates radicals in the photocatalytic reaction. However, since it is used topically on unbroken skin, this should not be an issue. Overall, it is considered to be an inferior product compared to Zinc Oxide as it is less effective in against long UVA rays and it causes a stronger whitish tint. Similar to Zinc Oxide, do exercise prudence with nanoparticles of titanium dioxide.
Ecamsule (Mexoryl SX) 290-400 nm
Mexoryl SX protects against the full range of UVA rays and part of UVB rays. It is photostable, and is minimally absorbed into the skin. Mexoryl SX rarely causes skin irritation and dermatitis. In its pure form, it is acidic but in beauty products, is neutralized by oranic bases, such as mono-, di- or triethanolamine. Ethanolamines can cause dermatitis. If you become allergic due to sunscreens containing Mexoryl SX, it could be because of the Ethanolamines. Just switch to one that uses a different neutralizing base. Sunscreens containing Mexoryl SX and Mexoryl XL (below) are exclusive to L’Oreal.
Drometrizole trisiloxane (Mexoryl XL)
There’s a lack of information online regarding Mexoryl XL. However, it is considered a safe and stable molecule. Mexoryl XL also absorbs UVA and UVB rays, and works synergistically with Mexoryl SX.
Bisoctrizole (Tinosorb M) 280-400 nm
TInosorb M acts as both chemical and physical sunscreen. It absorbs scatters and also reflects UVA and UVB rays. It is stable when exposed to sunlight and can even partially protect other chemical sunscreens from degradation. It is produced in the form of nanoparticles, but it is stable, poorly soluble and minimally absorbed by the skin and therefore should be relatively low in risk. However, as with other nanoparticles, the long term effects are still unknown. Tinosorb M rarely causes skin irritation, and is considered to be non toxic.
Bemotrizinol (Tinosorb S) 280-400 nm
Smilar to Tinosorb M, Tinosorb S also protects against UVA and UVB rays. It is also photostable and can partly protect other chemical sunscreens. It also rarely causes skin irritation, and is considered non-toxic.
So which is the best sunscreen ingredient?
I guess there isn’t one single perfect sunscreen ingredient we can depend on. There are many formulations in the market, and we should choose one that suits our needs and lifestyle. For me, I would go with a regular Zinc Oxide based sunscreen (not microfine). It seems to be the safest option. I can live with the white tinge or simply get one that is tinted beige. For swimming, it is best to use a chemical based sunscreen like Mexoryl SX and XL so that the sunscreen does not get washed away. Sunscreens are used to protect, so choose one that actually provides sufficient protection, rather than one that causes more damage!
References
http://www.physorg.com/news63466994.html
http://www.physorg.com/news177608158.htm
http://www.abc.net.au/news/stories/2008/12/18/2450030.html
http://www.healthychild.com/first-aid/sunburn-prevention-are-sunscreens-safe/
http://www.skincancer.org/understanding-uva-and-uvb.html
http://www.smartskincare.com/skinprotection/sunblocks/
http://www.savvyskin.com/zinc-oxide-vs-mexoryl-sunscreen-ingredients
http://www.healthhype.com/harmful-sunscreen-ingredients.html
http://www.bloggang.com/mainblog.php?id=pupesosweet&month=13-11-2008&group=6&gblog=20
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