Sunscreen is an essential way to protect your skin from the sun and prevent skin cancer, but there are many myths and misconceptions when it comes to its application.

Everyone 6 months and older, regardless of skin tone, should use it on exposed skin when they head outside (even on cloudy days).

Here are 25 facts about sunscreen that will save your skin!

1.
Physical (mineral) sunscreen ingredients (including the minerals titanium dioxide and zinc oxide) block and scatter the rays (like a shield) before they penetrate your skin.

2.
Chemical sunscreen ingredients (like avobenzone and octisalate) absorb UV rays (like a sponge) before they can damage your skin.

3.
People with sensitive skin should use mineral sunscreens containing either zinc oxide or titanium dioxide, as chemical ones can trigger skin irritation.

4.
A "Broad Spectrum SPF [value]" label indicates that the sunscreen you're buying can block both UVA and UVB radiation.

5.
UVB penetrates and damages the outermost layers of your skin. Overexposure causes suntan, sunburn and, in severe cases, blistering. UVB is connected to the Sun Protection Factor (SPF) on labels of sunscreen products.

6.
It's essential to apply sunscreen every day. UVB penetrates and damages the outermost layers of your skin.
The sun's rays can still damage the skin when it's cloudy, and it does not discriminate based on skin tone.
Research suggests that even sun exposure through a car window can up the risk for skin cancer.
Overexposure causes suntan, sunburn and, in severe cases, blistering.
You should still wear sunscreen even if you're indoors, as UV rays can still pass through window glass.
Look for an SPF of 30+ and reapply every two hours if you are in the sun.

Also read: How To Treat Sunburn

7.
Despite sunscreens blocking the sun's UVB light (which causes vitamin D production), numerous studies have concluded that using them won't lead to a vitamin D deficiency.

8.
Expired sunscreen actually means that the product will no longer protect you and it increases your potential for sunburns, sun damage and skin cancer. If you're using expired sunscreen, you're essentially just putting on a regular moisturizer and aren't getting any sort of UV protection.

9.
A sunburn sustained in the 1940s while climbing the Swiss Alps inspired chemist Franz Greiter to develop a ground-breaking product. His own experience inspired him to create Gletscher Crème, the first modern sunscreen, in 1946.

10.
One of the commonly missed areas for applying sunscreen is the lips.
Use a balm or other SPF product made specifically for the lips, and, just like the stuff you put on your face and arms every day, it should be broad-spectrum and have an SPF 30 or higher.

11.
Sunscreen is an important part of sun protection, but sunscreen alone isn't enough to keep you safe from harmful rays. You also can protect yourself with a wide-brimmed hat, sunglasses, sun-protective clothing and limiting your sun exposure during the most intense times of day, from 10 a.m. to 4 p.m.

12.
Oily sunscreens can block pores, causing acne breakouts.
Best ingredients: look for a non-comedogenic and oil-free sunscreen made with mineral sun-blocking ingredients like zinc oxide and titanium dioxide.
Worst ingredients: avobenzone, benzophenone, methoxycinnamate, and para-aminobenzoic acid (PABA) are all common chemical sunscreen ingredients that can cause pimples in acne-prone skin.

13.
It's best to apply sunscreen before you head outside—at least 15 to 20 minutes before sun exposure—because it needs time to soak in to be the most effective.
This rule applies regardless of what kind of sunscreen you use, be it chemical, mineral, or a combination formula.

14.
The reason why everyday sunscreen users tend to find avobenzone sunscreen irritating is that most (probably more than 90%) of sunscreen products with avobenzone have oxybenzone at the same time. The culprit of stinging and irritation is most likely oxybenzone instead of avobenzone.

15.
Avobenzone creates a defensive layer that soaks up the energy from whatever UV radiation you may be exposed to, then expels it before it can do any damage. It absorbs UVA radiation and converts it into heat, which is then released from the skin.

16.
Sunscreens that contain retinol not only protect your skin from the sun's UV rays but also prevent wrinkles due to retinol's anti-aging effects.

17.
While sunscreen does protect against UV rays, it is not a complete barrier. Tanning is caused by UVA rays, of which smaller amounts can still penetrate through sunscreen. This means you can still get a tan while wearing sunscreen.
However, it's important to note that a tan is actually a sign of skin damage.

18.
There's a term called "the shot glass rule" when applying sunscreen.
The "shot glass rule," for the unfamiliar, is a layman's way of making sure that you wear the proper amount of sunscreen. It states that the amount of sunscreen you put on your skin should be equivalent to a full shot glass, or about one ounce (29.6 milliliters).

19.
Reapply sunscreen at least every two hours, or more often if you've been sweating or swimming. A sunscreen may be water resistant, but no sunscreen is waterproof.

20.
You may need to apply sunscreen underneath clothing because some clothes have a poor ultraviolet protection factor (UPF).

21.
There's less chance of getting a white cast on your skin if you opt for chemical sunscreen — a white cast is a white residue you typically see after applying mineral sunscreens. But if you do use one, tapping or patting the sunscreen on your face, and letting it settle for a while, makes the white cast less noticeable.

22.
To prevent a white cast from appearing after applying sunscreen, reach for a chemical sunscreen that absorbs into the skin, rather than sits on top of it. Alternatively, if your skin is sensitive to chemical sunscreens, try using a tinted mineral sunscreen to combat white cast.

23.
Chemical sunscreen should be applied before your moisturizer, as your skin has to absorb it first to be effective. However, if you're using a physical sunscreen, you must put it after moisturizing since it needs to sit on top of your skin to achieve sun protection.

24.
Don't spray your face with sunscreen directly, or else you might breathe some sunscreen by accident. Instead, spray your hands with the sunscreen spray, and massage the sunblock onto your cheeks, forehead, and nose.

25.
The FDA and the American Academy of Pediatrics (AAP) recommend keeping newborns and babies younger than 6 months out of direct sunlight.
That's because infants are at greater risk than adults of sunscreen side effects, such as a rash.

May 27 is the national day to learn more about sunscreen and encourage your friends to use it too!

The more you know about this critical issue, the better you can protect yourself while still having fun in the sun.

What is UV?

Ultraviolet (UV) light is part of a family of radiations called the electromagnetic (EM) spectrum. UV is just beyond the violet end of visible light and has smaller wavelengths and greater energy.

As with all electromagnetic spectrum radiations, UV travels at the speed of light. Humans cannot see it, but some animals, especially some insects, can see UV light and have body markings that reflect UV light.

What is UV Radiation?

Sunlight sends a whole spectrum of light down to us here on Earth.

Infrared radiation is what heats us up. We may not see it, but we can feel it.

Ultraviolet radiation is at the other end of the light spectrum. UV radiation can burn and damage our skin without us ever becoming warm. That's why it is dangerous even on cloudy days.

Not all UV radiation from sunlight makes it to Earth. Most of it gets absorbed by our atmosphere. But two kinds of UV rays do break through. They are called UVA and UVB radiation.

What is UVA Radiation?

UVA radiation makes up 95% of the all the UV rays that make it to the Earth's surface. UVA penetrates deep into our skin and can even pass through glass.

UVA damages your skin, resulting in a tan. It is the primary radiation used in tanning beds. It causes almost all forms of skin aging, including wrinkles. UVA damages the collagen and elastin in the skin and also generates free radicals.

And recent research shows it doesn't end there. "UVA partners up with UVB to cause more serious problems, like skin cancer," says Saira George, M.D., a dermatologist at MD Anderson Cancer Center.

What is UVB Radiation?

UVB radiation makes up only 5% of the UV rays from the sun, but it is very high energy.

UVB does not penetrate as deeply as UVA, but it can wreak havoc on the top layers of your skin.

UVB damages skin cells and causes DNA mutations that can eventually lead to melanoma and other types of skin cancer.

UVB radiation from the sun also can cause cataracts.

Cataracts happen when proteins in your eye lens get damaged. The proteins start to collect pigments that cloud your vision.

What is SPF?

The sun protection factor (SPF) shows the degree of sunburn protection offered by a product. Note that this measure is only for UVB rays, and there is no specific rating for UVA rays, according to the FDA. (Again, a sunscreen's "broad-spectrum" label is what confirms that it protects against both UVA and UVB.)

What is UPF?

Ultraviolet Protection Factor (UPF) indicates how much UV radiation (both UVB and UVA) a fabric allows to reach your skin.

For example, a UPF 50 fabric blocks 98 percent of the sun's rays and allows two percent (1/50th) to penetrate, thus reducing your exposure risk significantly.

What you need to know: A fabric must have a UPF of 30 to qualify for The Skin Cancer Foundation's Seal of Recommendation. A UPF of 30 to 49 offers very good protection, while UPF 50+ rates as excellent.

Sources
American Academy of Dermatology / Houston Methodist - Mineral vs Chemical Sunscreen / Forbes / Everyday Heath / Skin Cancer Foundation - Sun Protection and Vitamin D / Cleveland Clinic / New York Times / New York Magazine / Skin Cancer Foundation - All about sunscreen / NBC News - 12 best sunscreens for acne prone skin / Charlotte Eye Ear Nose & Throat Associates / Yahoo News / InStyle / Colore Science - Does sunscreen prevent tanning / Colore Science - How often to reapply sunscreen / ABC13 / NBC News - Do you need to wear sunscreen inside? / National Library of Medicine / L'Oreal Paris / Skin Cancer Foundation - Sun-safe Babies / Houston Methodist - Is spray sunscreen effective? / Insider / MD Anderson / Skin Cancer