Sun’s Cream (Part 1)

Dew Abides homemade sunscreen
Courtesy of Flickr/Rachid Ahitass

Hormone disruptors or skin cancer? This is the decision I make everyday when choosing whether or not to apply sunscreen. And for someone who sizzles like a piece of bacon after ten minutes in the sun, it’s a real dilemma.

The problem is, of the fifteen FDA-approved sunscreen chemicals that absorb UV light, nine are known endocrine disruptors, meaning they interfere with hormones like estrogen, progesterone, testosterone, and thyroid — which can lead to developmental issues in growing children, infertility, and a higher risk of breast, ovarian, or prostate cancers.

Even scarier? That stuff can be found in blood, urine, and breast milk for up to two days after a single use.

Two mineral alternatives can protect skin by reflecting UV rays instead of absorbing them: zinc oxide and titanium dioxide. Unfortunately, commercial sunblock with those active ingredients is expensive and feels like toothpaste.

But what about homemade? Is it possible to mix up a functional sunscreen that doesn’t need a caulk gun for application?

In order to answer that question, I had to first figure out what SPF is required for safety’s sake. And what does SPF really mean?

Sun Protection Factor is a relative term that lets you calculate how long an application of sunscreen will be effective. The idea is to multiply the SPF by the number of minutes it takes you to burn — the answer is how long you should go in between slatherings. So if I burn in 10 minutes, an SPF 30 will last for 300 minutes. (10 x 30 = 300)

But as this Consumer Reports article points out, SPF doesn’t take into account the fact that UVB ray characteristics vary by location and time of day. And it doesn’t apply at all to UVA rays, so it’s not as precise as it seems.

They go on to say that “no sunscreen blocks 100 percent of UVB rays, and ultrahigh SPFs are not much more protective than SPFs of 30 or 50. SPF 15 blocks 93 percent of UVB rays. SPF 30 blocks 97 percent. The increase in protection is even more gradual after that, 98 percent for SPF 50 and 99 percent for SPF 100.”

Which means expensive, high-powered sunblocks instill a false sense of security. (Note: Watch the video in that Consumer Reports link for an interesting test on the advertised vs. actual SPFs of natural sunscreens.)

All this talk about sun blockage leads me to the other reason I’m changing my relationship with sunscreen — my body’s severe vitamin D deficiency. You can imagine the shock at my doctor’s discovery that I, an environmental scientist who spends a lot of time outdoors, had so little vitamin D that high-dosage supplements were immediately prescribed. A terrifying thought, since studies have shown folks with a severe vitamin D deficiency have 125 percent higher risk of developing dementia, among other health issues.

So, yeah, a little sun is in order.

But some protection is necessary, so it was off to the Dew Abides Test Lab to see if a moderate SPF 20 lotion could be hacked. The interwebs has some excellent peer-reviewed articles on the Sun Protection Factor of common oils that we have around the house, like coconut and peppermint.

Let me be clear, though. Homemade sunscreens will never have high SPFs like their chemical-filled counterparts, but I’m hoping to find a compromise that will do the job, when combined with regular application, a good hat and lightweight, protective clothing.

Stay tuned for a report of my results in the next post.

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