7 Things You Probably Didn’t Know About SPF

We took this photo outside to get that natural glow that comes from sunlight. This shot inspired this blog about sun protection, and healthier, younger skin.

The sun emits radiation: UVA and UVB rays. UV rays damage skin cell DNA and can lead to skin cancer.

The only way to prevent skin cancer is to protect yourself from the sun by:

• Applying Sun Protection Factor (SPF)

• Wearing protective clothing

• Straight up limiting sun exposure

Since we absolutely love the sun and most of us generally refuse to wear long sleeves and long pants in the summer (probably because we love a tan but sweat like a beast), let’s focus on some SPF facts. Here are 7 things that you probably didn’t know about SPF.

1. You can layer SPF — but it doesn’t work the way you think

You can layer SPF on top of SPF, but you’re not doing yourself any favors.

What the SPF numbers mean

• SPF 15 blocks 93% of UV rays

• SPF 30 blocks 97% of UV rays

• SPF 50 blocks 98% of UV rays

• SPF 100 blocks 99% of UV rays

So an SPF over 30, provides marginally more protection.

Sunscreens do not add up to more protection

Here’s the kicker. SPF limits a percentage of UV rays. So if you use a moisturizer with SPF 15 and a foundation with SPF 30, you don’t get SPF 45 protection.

Instead, SPF 15 + SPF 30 = SPF 30, regardless of which SPF you apply first.

You’re probably not wearing enough SPF

The SPF number gives you the promised protection if you apply it perfectly. That means a THICK layer of product. The industry assumes you’ll apply 2 mg/cm² — or about 4 ounces for your entire body. Take a look at this YouTube video by Wayne Goss which lets you see how much you actually need to put on.

Unfortunately, the average consumer only applies 1/4 to 1/2 of the right amount of liquid sunscreen to get the advertised amount of protection. So, most people only get an SPF 7.5 to 15 when they apply a product of SPF 30.

And it’s worse with powder products. The average consumer only applies 1/14. So, you’re probably only getting an SPF 2 when wearing an SPF 30 powder.

In other words, while an SPF 100 gives you slightly more protection than SPF 50, you may get more or the same amount of protection than SPF 50 depending on your application.

SPF Protection	Perfect Application	Average Consumer
SPF 50	SPF 50	SPF 12.5-25
SPF 100	SPF 100	SPF 25-50

But of course, having more SPF never hurt anyone.

2. Chemical vs. physical sunscreens

Sunscreen generally refers to chemical sunscreens, whereas sunblock is a physical sunscreen.

Chemical sunscreens absorb into your skin and convert the sun’s rays into heat. You generally need to apply this 15-30 minutes before sun exposure and you need to rub it in. You’ll see active ingredients like oxybenzone, avobenzone, octinoxate, and octisalate.

Chemical sunscreens are more common. And a 2020 FDA report found that four popular active ingredients were absorbed into the bloodstream. There’s no evidence that it’s unsafe, but this new report definitely supports the need for additional studies. We haven’t experienced any negative side-effects from them, and the FDA recommends continuing to use chemical sunscreens.

Here are our two favorite chemical sunscreens:

Physical sunscreenssit on the surface of your skin and deflect the UV rays. There’s no down time like chemical sunscreens, and starts working immediately. Common active ingredients include zinc oxide and titanium dioxide, which is why they’re sometimes called mineral sunscreens.

They do not absorb into the body, but since they sit on the surface of the skin, you may see a white tint with some formulas, which doesn’t look good — especially under makeup.

Our favorite physical sunscreen is from Bare Republic because they perform well under makeup. And we haven’t had a problem with any white cast.

3. You need broad spectrum sunscreen

You shouldn’t be choosing between UVA or UVB protection. They both contribute to skin cancer. You need a product that blocks all UV rays. Look for a product that provides broad-spectrum SPF.

4. You need sunscreen on cloudy days

On overcast days, UV radiation can go right through thin clouds. Or they can bounce off clouds and actually emit stronger radiation, according to Vernon Carr, a national manager at the Bureau of Metrology.

5. You need sunscreen when you’re not in the sun

Even when you’re sitting in the shade, you still need sun protection.

• Soil reflects 4%-6% of UV rays

• Grass reflects 2%-5% of UV rays

• Concrete reflects 8%-12% of UV rays

• Asphalt reflects 4%-8% of UV rays

And if you’re at the beach, sand reflects 15% while seafoam reflects 25%, according to the World Health Organization. And let’s not talk about how sun reflects off buildings, cars and glass.

Basically, everything reflects some amount of UV rays. So don’t underestimate your UV exposure — even when you’re chilling in the shade.

6. You need sunscreen in the winter

You need sun protection in the winter too. The sun doesn’t just emit fewer UV rays when it’s cold outside. And fresh snow can reflect up to 90% of UV radiation and double your UV exposure.

7. You need to reapply sunscreen

Unfortunately, sunscreen is not a set it and forget it product. And forget the myth that SPF 15 lets you stay in the sun for 15 hours. It’s about the amount of sun exposure, not time.

Other factors that can break down your protection include:

• Swimming. Water breaks down sunscreen.

• Sweating. Those little beads of sweat take some of your sunscreen with it.

• Exposure to the sun. Chemical sunscreens break down as it absorbs UV light.

• Any contact with your skin. If you touch your face, towel dry your body, or just brush up against something, it can remove some of your sunscreen.

• Clumping. Physical sunscreens like to clump on the skin over time.

No matter what type of sunscreen you use, you’ll probably need to apply every 2-3 hours, depending on what you’re doing and where you are.

If we’re not directly in the sun all day, our writers like to touch up makeup midday by applying a powder SPF to help absorb oil and add some more sun protection.

But on days that we’re going to be in the sun, one writer says she may skip the liquid makeup altogether and use a tinted moisturizer with a high SPF, one of those powder SPFs to absorb oil, and finish off with a SPF setting spray that she can easily reapply, like Coola.

How much SPF do you need?

The recommended SPF varies depending on who you ask. But most people agree that SPF 15 is the minimum. Here is a snapshot on where the health authorities stand:

• The American Academy of Dermatology recommends SPF 30+.

• The Skin Cancer Foundation recommends SPF 15 every day and SPF 30 if you’re going to be out in the sun.

• The FDA, WHO, and the CDC recommend SPF 15+.

Most people know that the sun causes skin cancer. But UV rays also contribute to premature skin aging. So wearing SPF will make your skin healthier and look younger too! Win-win.