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Do UVA Rays Cause Tanning?
[caption id="attachment_17642" align="aligncenter" width="600"] The UV emission of the sun. Pretty; scary. Get it?[/caption]
[caption id="attachment_17643" align="alignright" width="300"] CPD generation.[/caption]
It is a well-established fact that UVB rays cause direct DNA damage in the form of cyclobutane pyrimidine dimers (CPDs), which are when the molecular bases incorrectly link together with bases from the same strand of DNA, rather than those of the opposite strand. This in turn, leads to melanogenesis and the consequent darkening of the skin.
It is also a well-established notion that UVB rays are solely responsible for tanning, while UVA rays are responsible for “aging.” Hundreds of health and beauty blog authors oversimplify the idea to: UVB means “Burning” and UVA means “Aging.” I’m sure all of you have seen that phrase. This notion however, is not accurate.
Both UVA and UVB Cause Tanning
While UVA irradiation may not induce melanogenesis, it will still increase the darkening of the skin. Therefore, it has a similar cosmetic effect as UVB-induced tanning, albeit a less dramatic one. There are two main avenues through which UVA achieves this effect. Firstly, UVA rays will oxidize and/or polymerize already existing melanin and transform it to become even darker and more apparent. This occurs immediately upon exposure to UVA rays.
Secondly, UVA stimulates initially colorless melanogenic precursors such as DHICA and 6H5MICA and changes them into a dark-colored pigment. This phenomenon occurs outside of melanocytes, which are the cells responsible for melanin production.
What Does This Mean?
UVA irradiation actually DOES cause immediate darkening or “tanning” of the skin. So ironically, while many people think that their “tans from yesterday at the beach” are because of UVB irradiation and therefore, additional melanin, these tans may actually be from UVA irradiation. And because the melanogenic precursors mentioned above don’t provide an additional level of UV protection (unlike actual melanin), it’s rather dangerous to think that, “Oh, this tan is going to provide extra protection against the sun.”
***Keep in mind that the darkening from UVA irradiation does tend to not be as pronounced as that induced by UVB irradiation.
What Can You Do to Protect Yourself?
[caption id="attachment_17644" align="alignright" width="300"] Here's what the sun does to polypropylene rope. This isn't pretty; just scary.[/caption]
You absolutely have to use sunscreens that provide good to excellent protection against UVA rays. I really hate that many experts claim that, “If your sunscreen provides broad-spectrum protection, you can rest assured that you’re getting adequate protection from UVA rays.” For example, I recently read a review on Beautypedia ran by Paula Begoun, that generally speaking, 2% titanium dioxide is sufficient to provide adequate broad-spectrum protection. WHAT?! And then in a video by Dr. Neal Schultz, he stated that it doesn’t matter what concentration of UV filters is present because, “All chem.-free sunscreens have UVA protection.” The relevant question begins at 6:25.
Now, if you’ve been one of my longtime readers, you’ll know that I’m a big fan of both of these pioneers. However, that doesn’t mean I agree with everything they say. Yes, all chem.-free or inorganic sunscreens provide SOME form of UVA protection, but that doesn’t tell me how much. There seems to be this incorrect perception that your sunscreen provides “broad-spectrum” protection, or it doesn’t. As if, you get either 100% UVA protection or none at all.
Let me tell you, that rationalization is WRONG! UVA rays are just like UVB rays in the sense that UV filters provide a percentage of protection against them. And while UVA rays are less potent (due to having less energy as a photon with a longer wavelength) than UVB rays, there is so much more of the former present in natural sunlight than the latter: the UV component of the sun is made up of approximately 94% UVA rays and 6% UVB rays. That’s almost a twenty-fold difference!
Be Diligent and Vigilant
So if you want to trust these recommendations, then by all means, no one can stop you. But my personal recommendations are as follows:
If you’re using an organic sunscreen, look for ones that contain at least 3% avobenzone that’s been stabilized by good amounts of octocrylene and/or oxybenzone, assuming that you don’t have access to Tinosorb S or M. Of course, look for high amounts of UVB-absorbing UV filters as well. Avoid sunscreens that contain both avobenzone and octinoxate.
If you’re using an inorganic sunscreen, look for ones that contain “high” amounts of UV filters. I can’t make a blanket recommendation as to which number is sufficient because “high” depends on a variety of factors such as which UV filters are present, how much of each is present, and whether or not organic sunscreens are present as well. But ideally, use the highest concentrations of inorganic UV filters that you can accept aesthetically.
I hope this was an informative post and make sure to enter my giveaway! It’s way to help me, help you!