Sun Protection: Is your sunscreen protecting you?

 

 A sunscreen with a high SPF rating may not, and in fact probably is not, protecting you against the longer wave length UVA rays. UVA rays are present from sunup to sundown, penetrate glass and clouds and enter the dermis. They are 1000 times more prevalent than UVB. They are called the aging rays because they cross-link collagen and elastin, turn melanin darker and cause hyper and hypo-pigmentation and broken capillaries. They also damage DNA, destroy Langerhans cells and compromise immune function. I believe, but of course this is just a guess, that we can attribute at least part of the increase in the prevalence of rosacea to the fact that people are getting more exposure than they should, because they believe that their "SPF 45 (and higher)" products are providing adequate protection. At any rate, in particular those of us who are rosacea-prone should be aware that UVA protection is a year round affair. My mnemonic is: UVA means U must be Vigilant Always.

 

 

This leads us to the all-important topic of testing. The SPF rating system tests burning rate times between protected and unprotected skin, and is a fairly simple test to perform. Since the effects of aging are longer-term the testing is much more problematic, though a test adopted by Japan and Europe, called Persistent Pigment Darkening, (PPD) uses essentially the same methodology as is used in SPF testing. L'Oreal Research presented such a PPD model in a recent study.

 

In the L'Oreal study human volunteers were exposed to 330-440 nm of light 3 times a week for 4 weeks. Exposed sites were compared with nonexposed sites, exposed sites protected with a broad UVA absorber, and exposed sites to which a sunscreen vehicle had been applied. Various parameters related to UVA exposure and early alleged alterations leading to photoaging were measured. Those parameters included pigment darkening, stratum corneum thickening and changes in elasticity.

 

 

Chemical sunscreens work by absorbing UV rays, lowering energy levels, then releasing the energy as heat.

 

Avobenzone (aka Parsol 1789) has been used in sunscreen products for a number of years for its ability to offer sun protection in the higher UV ranges, up to 400 nm (the UVA range is 320-400 nm). Unfortunately avobenzone degrades quickly in light, and 30 minutes of exposure will significantly reduce its effectiveness. It is sometimes combined with photostabilzers like octocrylene to extend its efficacy period.

 

Mexoryl (TM) SX is the active ingredient in a chemical sunscreen known as Anthelios that is in widespread use in Canada, Europe and Japan. L'Oreal holds the patent on it, and it has recently been approved by the FDA for sale in the US.   It offers protection against the shorter wave lengths of UVA, showing greatest efficacy in the 340-350 nm range. 

 

 

Mineral sunblocks work by reflecting or scattering energy rays. 

Titanium dioxide