We all know that experts (and moms) agree: When you go out into the sun for extended periods of time, you should wear sunscreen to protect your skin from the sun’s harmful rays. But this simple statement comes with lots of questions, for example, what are the best sunscreens? Should you always wear sunscreen? How important is sunscreen, really? The more informed you are, the better decisions you’re able to make. When it comes to choosing sunscreen and taking care of your skin, no question is too silly to ask!

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What does SPF stand for?

You’ve seen the label on the bottles at the drugstore, but what does sunscreen SPF mean and why is it important? SPF stands for “Sun Protection Factor” and it is a measurement of how well a particular sunscreen protects you from the sun’s rays. For example, an SPF of 25 means you can stay in the sun 25 times longer than you can without protection before burning.

The higher the number, the more protected you are, but SPF does not increase proportionally by number. An SPF of 2 absorbs 50% of ultraviolet (UV) radiation, while an SPF of 15 absorbs 93% and an SPF of 34 absorbs 97%. Sunscreens with an SPF of 30 or higher do not vary by a large degree in their ability to absorb radiation. The next question you might have, then, is how does sunscreen actually work to protect you from sun damage?

How does sunscreen work?

Sunscreen is made up of organic and inorganic ingredients that protect your skin from the sun’s ultraviolet radiation. The organic ingredients work to absorb UV radiation, dissipating the rays as heat. Some examples of these are oxybenzone and octyl methoxycinnamate (OMC). The inorganic ingredients in sunscreen work to scatter the UV rays. These include titanium oxide and zinc oxide.[1]

What is the difference between UVA and UVB?

There are two main types of UV radiation that concern us: UVA and UVB rays. UVB rays can harm the skin’s outer layer, called the epidermis, and cause reddening and sunburn. Some lesser forms of skin cancer are caused by UVB accumulation over the years.

UVA rays are the more dangerous of the two types of UV rays, as they are strong enough to reach past the skin’s epidermis, down to the dermis, and can damage collagen and elastic tissue. UVA rays also cause skin darkening, which is a sign of DNA damage, and can lead to more serious forms of skin cancer. Most sunscreens block only UVB rays, and SPF is only a measure of UVB protection, though some sunscreens also protect against UVA radiation.[2]

How to choose sunscreen?

Armed with the above knowledge of UVA vs. UVB rays, you can infer that a sunscreen that protects against both types of radiation is preferable to a sunscreen that protects against only one type. What are some additional considerations when choosing a sunscreen? Skin tone, skin type, level of activity, interaction with water, and method of application are some good things to think about.

For example, the best sunscreen for fair skin is one with an SPF of 30 or higher, while sunscreen for dark skin needs at least an SPF of 15. The best sunscreen for sensitive skin and also the best sunscreen for kids is one that contains zinc oxide or titanium oxide, which are a bit gentler. The best sunscreen for dry skin is one that also acts as a moisturizer. Meanwhile, the best sunscreen for acne prone skin is one that has a gel formula, which is less likely to cause breakouts. Spray sunscreen could be a good option for older folks who might have trouble applying sunscreen. If you know you’re going to be sweating or swimming this summer, be sure to check that your sunscreen is water or sweat resistant. It’s always a good idea to look up sunscreen ratings to compare brands, too.

How to apply sunscreen?

It might seem straightforward, but some tips for applying sunscreen could come in handy. Too much or too little can be either annoying or unsafe, so squirting a random amount into your hand isn’t the best approach. Instead, try using about one ounce of sunscreen for your entire body. That’s about the size of a ping pong ball. However, it’s better to err on the side of too much sunscreen rather than too little.

You generally want to apply sunscreen about 30 minutes before going out into the sun, and reapply every 2 hours, as well as right away after swimming, even if your sunscreen if water resistant. Protect your lips by using a balm or chapstick that contains sunscreen!

Finally, should you wear sunscreen every day? The answer is YES! Dermatologists recommend applying one ounce or more of sunscreen every day you go outside. Even on a cloudy day, 80% of UV rays can penetrate your skin. Make wearing sunscreen part of your daily routine.

What are some sunscreen alternatives?

Whether you wear sunscreen every day or not, it’s also important to consider other ways of protecting your skin from the sun. You can shade yourself under trees with large spreads of dense foliage, and be attentive to how much time you’re spending in the sun.

Natural alternatives to sunscreen include sun protective clothing, such as hats with brims at least 3 inches wide. These broad-brimmed hats are estimated to provide protection equivalent to SPF 5 for the places on your body it protects—the nose, ears, and neck. Also consider wearing clothing with an Ultraviolent Protection Factor (UPF) rating. An item of clothing’s UPF rating is very similar to a sunscreen’s SPF rating: a garment with UPF 50 blocks against 98% of UV rays.[3]

Why should you wear sunscreen?

With all this discussion on sunscreen, it’s important to understand why sunscreen is so crucial. Scientific evidence proves that wearing sunscreen is a behavior that can minimize and reduce your chances of getting skin cancer, along with other protective measures like wearing UPF-rated clothing and avoiding prolonged sun exposure. Also, sunscreen can help prevent brown spots and skin discoloration, as well as prevent wrinkled, prematurely aged skin.[4] It’s not just an empty saying, it’s a motto to live by: Always wear sunscreen!

[1] https://www.loc.gov/rr/scitech/mysteries/sunscreen.html

[2] http://www.consumerreports.org/cro/magazine/2015/05/what-does-spf-stand-for/index.htm

[3] http://www.melanomafoundation.org/prevention/clothing.htm

[4] http://www.huffingtonpost.com/2013/06/19/sunscreen-benefits_n_3464687.html