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Sun Protection 101

Sunscreen vs Sunblock

Sunscreen uses organic and inorganic chemical filters to prevent the sun’s rays from penetrating the deeper layers of the skin. Common, sun-filtering ingredients in chemical sunscreens are oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate.

Sunblock uses mineral filters, usually zinc oxide or titanium dioxide, which reflect or scatter the rays to prevent them from reaching the skin.

What is SPF and how does it work?

SPF stands for Sun Protection Factor, and refers to the ability of a sunscreen to block ultraviolet B (UVB) rays, which are responsible for burning the surface of the skin. However, SPF does not block ultraviolet A (UVA) rays, which penetrate deep into the layers of the skin, causing skin damage, aging, and skin cancer, specifically, squamous cell carcinoma.

When thinking about SPF, most people would probably assume SPF 30 is twice as effective as SPF 15, but that’s actually not the case.

  • SPF 15 blocks about 93% of UBV rays,
  • SPF 30 blocks 97%,
  • SPF 50 block 98%, and
  • SPF 100+ blocks about 99.1%.

So you can see that anything higher than SPF 50 can get fairly unnecessary—it’s usually just more expensive (but potentially more toxic, which I’ll talk more about in a minute.)

Theoretically, the SPF number can also help you determine how long you can stay in the sun. If you can normally stay in the sun for 10 minutes before burning, then applying a sunscreen with an SPF 10 will allow you to stay in the sun 10x longer without burning (100 min).

Do we need sunscreen?

There are a couple ways to look at this question: while sunscreen can protect us from cancer-causing UV rays, it may  also be changing our behaviour and therefore increasing our exposure to the sun.

First, it’s no secret that melanoma is on the rise, and according to the National Cancer Institute, the rate of melanoma cases have tripled in the past 35 years. Although there is speculation as to whether or not the sun is the primary cause of this increase, melanoma can  be caused from the overexposure of UVB and, more specifically, UVA rays.

The problem with the majority of sunscreens is that they don’t provide adequate UVA protection, and even those that do, are just not enough because avobenzone, the main UVA filter added to almost all chemical sunscreen, breaks down in the presence of sunlight. So yes, we need sunscreen to protect us from the potentially damaging effects of the sun, but sunscreen alone is not sufficient.

On the other hand,“problems lie in the behavior of individuals who use sunscreens to stay out longer in the sun than they otherwise would.” Staying in the sun for longer periods of time is increasing our exposure to harmful UVA rays.

Is sunscreen toxic?

The BIG question! While many dermatologists are still saying no , and continue to recommend sunscreen “whole heatedly,” the Environmental Working Group (EWG) has a different opinion.

Sunscreen’s active ingredient comes in the form of chemical and mineral filters. It’s the chemical sunscreens that are causing need for concern.

According to the EWG,

[chemical sunscreens] include a combination of three to six of these active ingredients: oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate. The most problematic of the sunscreen chemicals used in the U.S. is oxybenzone, found in 80 percent of chemical sunscreens. EWG recommends that consumers avoid oxybenzone because it can penetrate the skin, cause allergic skin reactions and may disrupt hormones.

In one study, based on a sample of more than 2500 adults and children, 96% of them were detected to have oxybenzone in their systems.

Like I mentioned early, higher SPF doesn’t necessarily mean better protection from the sun, and the EWG advises to avoid sunscreens with high-SPF because they require higher concentrations of sun-filtering chemicals than low-SPF sunscreens. 

This study from Harvard states, “The sun protection factor (SPF) you see on the label of sunscreens is misleading. It’s not a measure of total sun protection but of protection against sunburn from UVB light.” They advise consumers to look at the ingredients instead of the SPF, and suggest that “the lotions containing zinc oxide and titanium dioxide may be the best bet.”

There is also speculation as to whether or not the sun is causing this spike in skin cancer, or the over-use of sunscreen itself. This question points to a certain sunscreen ingredient, vitamin A, and the EWG advises to avoid sunscreens that contain Vitamin A (labeled retinyl palminate).

The sunscreen industry adds a form of vitamin A to nearly one-quarter of all sunscreens. Retinyl palmitate is an anti-oxidant that slows skin aging. But federal studies indicate that it may speed the development of skin tumors and lesions when applied to skin in the presence of sunlight.

Although no sunscreen seems to be without its risks, sunblocks that use these mineral filters are considered safe, “non-toxic” options. 

Mineral sunblocks use zinc-oxide and titanium dioxide to reflect or scatter UV rays. They do not permeate the skin, and are stable in the presence of sunlight.  Zinc-oxide is the optimal ingredient in sunblock because it provides strong sun protection with few health concerns; it doesn’t break down in the sunlight, and offers good protection against UVA rays!

Nano-zinc vs Non-nano zinc. Are they safe?

A nanometer is about one hundred thousand times smaller than a human hair. There is concern that zinc nano-particles can be absorbed into the skin and then into the blood stream. Turns out, there are no studies out there proving that nano-particles of zinc oxide can penetrate the human skin. Instead, there’s a lot of research proving quite the opposite

Cosmetically, nano-zinc is a better option because when applied, it doesn’t leave behind white film (you know, that life-guard look?) Personally, and based on my own research, I feel comfortable using nano-zinc and have used it in the sunscreen that I’ve made for our trip. If you don’t feel comfortable using nano-zinc, use non-nano zinc which has larger particles.

Keep in mind, zinc-oxide doesn’t go without its dangers either. When inhaled, it can damage the lungs and enter the blood stream (so don’t be a silly-billy and wear a mask when making your own).

What oils naturally contain SPF?

Many oils are already naturally high in SPF! So even before adding the zinc oxide to your lotion/butter, it will already have an SPF of at least 2. In my sunblock, I usually use avocado oil because it has an SPF as high as 15!


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