How Sunscreen Works And How To Use It: Plus A Buyers Guide To Healthy Sunscreen

May 11, 2020 By

If you’re like many people, you slather on sunscreen before you go out. After all, you want to protect your skin from sun exposure. 

But have you ever thought about how sunscreen works? Understanding how sunscreen protects your skin will help ensure you’re using it the right way. 

There are two types of sunscreen: chemical and mineral (also known as physical). 

Here’s a quick look at both types of sunscreen and how their active ingredients help shield your skin from the harmful effects of the sun’s rays.

Your Skin And The Sun

To get a good idea of how sunscreen works, it helps to first understand how your skin protects you.

There are three main layers to your skin. Two of these layers are affected by the sun’s UVA and UVB rays. 

The top layer is known as the epidermis. The epidermis contains melanin, which is a pigment. The more melanin you have, the darker your skin will be. If you don’t have as much melanin, you’ll be at a higher risk for sunburn. Signs of sunburn include pain, blisters, itchy skin, and extreme redness. Some people even get chills or goosebumps.1

Below the epidermis is the dermis, which contains blood vessels and nerves.2 This layer is also affected by the sun, but in a different way — keep reading to find out how.

Protecting Your Skin From Ultraviolet Radiation: What’s The Difference Between UVA And UVB Rays?


Ultraviolet, or UV rays, are actually good for your body in small doses. They help stimulate the production of vitamin D. This vitamin makes it possible for the human body to absorb calcium, which promotes strong, healthy bones.3 UV rays can even help sterilize wounds.4

But UV rays can also do serious damage to the skin. There are two types of UV rays —UVA rays and UVB rays. 

UVA rays penetrate the skin deeper than UVB rays, reaching as far as the dermis layer of the skin. Too much UV radiation can disrupt skin cells,  affecting both the way skin looks and the way cells grow. Too much UV radiation  also robs your skin of elasticity, leading to a leathery, wrinkled appearance.5

The older you get, the harder it becomes for your skin to repair itself from UV damage. Sun damage may lead to more wrinkles, or even much more serious skin health and skin issues.6

Why Is Sun Protection Factor (SPF) So Important?


All sunscreen products have the SPF, or Sun Protection Factor, on their label. SPF is a measurement of how effective the sunscreen is in protecting the skin against UVB rays. These are the UV rays that lead to sunburn.7

Experts typically recommend using sunscreen with an SPF in the 15 to 50 range. The number is an indication of the percentage of UVB rays the product will block. 

An SPF 15 sunscreen blocks about 93 percent, while an SPF 50 sunscreen blocks 97 percent. There is no SPF that can completely block all of the sun’s rays.8

But SPF is significant in another way. It’s designed to give you an idea of how long it will take for UVB rays to make your skin red if you use sunscreen as directed. 

For example, SPF 30 means it will take your skin 30 times as long to burn due to UV radiation compared to not using any sunscreen at all.9

Note: If you see a sunscreen product with an SPF of between 2 and 14, it must also carry a warning label. This label must state that while the product may help protect against sunburn, it won’t protect you against premature aging or severe skin damage.10

What Is Broad Spectrum Sunscreen?


You’ve probably run across the term “broad spectrum” when shopping for sunscreen. It’s not just a fancy marketing term. It means the sunscreen provides both UVA and UVB protection. 

Broad spectrum sunscreen is the best choice because it helps protect against sunburn as well as premature wrinkles and age spots. Broad spectrum sunscreen is designed to help protect you from UV radiation and its  potentially serious health risks.11

Check Your Sunscreen Ingredients: What’s The Difference Between Mineral Sunscreens and Chemical Sunscreens?

There are two main kinds of sunscreen you’ll see on your grocery or drug store shelves: chemical sunscreens and mineral sunscreens.

Chemical sunscreens, as the name implies, are made of chemicals that are designed to absorb UV radiation before it can get into the skin. They trap the rays and release their energy in the form of heat. They’re typically thinner than mineral sunscreens, and you can even  apply them by spraying.12

Mineral sunscreens (also known as physical sunscreens), on the other hand, typically use two main active ingredients, zinc oxide and titanium dioxide. These minerals shield the skin from UV rays, forming a physical  barrier that disperses the UV waves so they can’t penetrate the skin.13

Should You Look For Mineral Or Chemical Sunscreens?


Zinc oxide and titanium oxide are considered to be both safe and effective. However, scientists have raised concerns about some of the ingredients found in chemical sunscreens. 

Certain chemicals found in these products, such as octocrylene, ecamsule, oxybenzone, and avobenzone, can be absorbed into the skin — sometimes making its way into urine, blood plasma, and even breast milk. Further research is needed in order to determine whether this absorption is harmful.14

If you’re concerned about the potential for chemical absorption, you should probably consider purchasing mineral sunscreens instead. Ask your dermatologist what they’d recommend.

Water-Resistant Vs. Waterproof Sunscreen

Have you ever noticed that sunscreen labels no longer say they’re “waterproof,” but “water resistant” instead? The U.S. Food and Drug Administration (FDA) mandated this change in 2013. The reason is that once you sweat or swim, you quickly lose sunscreen protection. There is no sunscreen that can protect your skin completely once it gets wet.15

How To Apply Sunscreen Correctly, And Why You Should Re-Apply It Frequently


Because no sunscreen is waterproof, that makes it critically important to remember to reapply sunscreen if you’re going to be outside for an extended period of time. Whether you’re sweating while playing sports, or you plan on taking a dip in the pool or ocean, you need to dry off and then put on more sunscreen right away.

A good rule of thumb is to reapply sunscreen every two hours when you’re outdoors – earlier if you sweat or swim. You’ll want to be meticulous with application so you don’t miss any spots. Start at the top with your left ear and then work downward, covering the entire left side of your body down to your left foot. Then, starting with the right foot, work back upward to cover the right side of the body.16

Have Questions About Sunscreen? Talk To A Dermatologist

There are hundreds of different sunscreens out there. You have so many options, in fact, it can get overwhelming. If you’re not sure what type of sunscreen will be best for you, talk to a dermatologist. They should be able to give you a reliable recommendation, and they can explain whether chemical or mineral sunscreens would be best for you.

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