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Staying Safe in the Sun: A Breakdown on Sunscreen

Brooke McKelvey

Published in Lifestyle

10 min read

May 20, 2022
a person applying sunscreen
a person applying sunscreen

Depending on where you live, summer is right around the corner or already in full swing. And with warmer weather, we’re looking forward to some grilling, swimming, and getting more of the sunshine vitamin. But before you head out, make sure you’re taking the proper precautions to stay safe in the sun

It’s important to protect your skin from the harsh effects of the sun’s rays, including premature skin aging and sun damage to your skin cells that can lead to skin cancer. One of the most effective ways to do this is to wear sunscreen. But what is sunscreen, and how does it work?

Read on to learn more about how sunscreen works, what the active ingredients are, and how much of the lotion (or spray) you should be applying to protect yourself from harmful UV rays.

How Does Sunscreen Work?

Person applying sunscreen

There’s some debate about the origins of sunscreen, but some experts believe that it dates back to ancient Egypt, where Egyptian women were known to apply oils and dyes to their skin to protect against harsh sunlight. Others suggest that the first evidence of modern sunscreen was discovered on a shipwreck in the 18th century.

Regardless of its exact origins, one thing is clear: sunscreen has always played a vital role in protecting us from the sun's harmful UV rays.

Over the years, new research and advances in technology have made it more effective than ever at blocking harmful UV rays and preventing skin damage. There are countless types of sunscreen available, each specifically tailored to suit different needs and preferences. Whether you want high SPF coverage for extended outdoor activities or mineral-based sunscreen gentle on sensitive skin, there is no shortage of options.

Several different formulations of sunscreen have been developed, including chemical sunscreens that absorb UV light and physical sunscreens with protection from both direct and reflected light.

Chemical sunscreens work by reducing the amount of UV radiation that penetrates the outer layers of our skin, reducing the risk of sunburns and skin cancer.

Physical sunscreens, also known as mineral sunscreens, use minerals like zinc oxide or titanium dioxide to reflect sunlight away from your body. They block harmful ultraviolet rays before they can do any damage. 

Despite some recent controversy around the safety of certain chemicals in sunscreen, it remains a popular and essential tool for protecting against skin cancer and premature aging. 

Why Sunscreen is So Important

Unlike a pair of sunglasses or a wide-brimmed hat, sunscreen permeates deeply into the skin and defends against harmful UV rays from all angles.

Wearing sunscreen every day can help to prevent premature aging, wrinkles, and leathery skin. And if you spend a lot of time outdoors—whether it's for work or play—ensuring that you're wearing sunscreen is crucial to avoid skin damage.

To ensure it's most effective, apply sunscreen liberally and evenly to all exposed areas of the skin, and reapply it every two hours or after swimming or sweating.

The Benefits of Using Sunscreen

Applying sunscreen to face

Lower your cancer risk, and prevent a sunburn... what else can sunscreen do for you? Its primary benefit is preventing skin damage caused by ultraviolet (UV) light.

UV light is a type of radiation invisible to the human eye but can be harmful to the skin. There are two types of UV radiation: UVA and UVB. UVA radiation is associated with premature skin aging, while UVB radiation is the primary cause of sunburn. 

Breaking Down UV Radiation

Both UVA and UVB radiation can also contribute to the development of skin cancer. The ingredients in sunscreen work to absorb, reflect, or scatter UV radiation to protect the skin. It is crucial to choose a sunscreen with an SPF of at least 15 to ensure adequate protection. In addition, it is important to reapply sunscreen regularly, especially if you are swimming or sweating. You can help protect yourself against UV radiation's harmful effects by taking these precautions.

Broad-spectrum sunscreen (usually physical or mineral sunscreen) typically protects against both types of rays. Sunscreen works by absorbing, reflecting, or scattering sunlight. The active ingredients in sunscreen absorb the UV rays and convert them into heat, which is then released from the skin.

Titanium dioxide and zinc oxide are two common ingredients that reflect or scatter sunlight. Sunscreen with an SPF of 30 or higher can block 97 percent of the sun's UVB rays [SOURCE].

However, it is essential to remember that no sunscreen can block all sun's UV rays, so it is still important to limit your time in the sun, wear protective clothing, and avoid peak sun hours.

Can You Tan with Sunscreen?

Want to protect yourself from sun damage without ruining your chances of getting a nice tan? There is a lot of conflicting information about whether you can still tan when you wear sunscreen. Some research claims that applying sunscreen prevents UV rays from reaching your skin, also preventing any tanning. 

Others point out that the type of protection provided by sunscreen only goes so far. Even if some UV rays do get blocked by the sunscreen, plenty can still penetrate your skin, creating the conditions for a healthy bronze glow.

Ultimately, it seems that the truth about tanning depends on various factors, including your skin type, how much time you spend in the sun, and what type of sunscreen you use. So if you're determined to get a tan this summer, make sure you take proper precautions and do your research before spending hours soaking up the sun. 

Sunscreen and Vitamin D Absorption

Rubbing in sunscreen

As you may have read in our article on vitamin D, whether or not sunscreen affects vitamin D absorption is a hotly debated topic. Because sunscreen blocks UV light, you can technically deduce that it inhibits vitamin D production.

But some studies indicate sunscreen cannot significantly influence vitamin D levels in your bloodstream.

However, we need more research to fully understand the complex relationship between sunscreen and vitamin D absorption. 

Regardless of what the science ultimately reveals, one thing remains clear: maintaining healthy levels of vitamin D is essential for optimal overall health. Whether you wear sunscreen or not, it is important to get enough sun exposure to support strong immune function and disease prevention. 

Understanding the Active Ingredients

There are two primary active ingredients in a sunscreen: chemical absorbents and physical blockers. Chemical absorbents work by absorbing ultraviolet (UV) radiation and converting it into heat. The most common chemical absorbents are avobenzone, octisalate, octocrylene, homosalate, and oxybenzone. 

Physical blockers work by reflecting or scattering UV radiation away from the skin. The most common physical blockers are titanium dioxide and zinc oxide.

Both types of ingredients effectively protect your skin from UV damage; however, physical blockers are generally seen as more effective than chemical absorbents.

In addition, physical blockers are less likely to cause skin irritation and are less likely to be absorbed into the bloodstream.

Does the SPF Number Matter?

SPF 50

SPF, or sun protection factor, measures how well a sunscreen will protect your skin from ultraviolet (UV) rays. To a certain degree, the higher the SPF number, the greater the level of protection.

For example, an SPF 30 sunscreen will filter out 97 percent of UV rays, while an SPF 50 sunscreen will filter out 98 percent of UV rays. However, as we mentioned before, no sunscreen is 100 percent effective, so all those labels with 50+ SPF numbers may not be that much better.

In addition, higher SPF numbers do not necessarily provide better protection against all types of UV radiation. 

For instance, an SPF 15 sunscreen may block more than 90 percent of UVB rays but only about 60 percent of UVA rays. It’s a good idea to read the labels to see what you’re getting. 

Some FDA Guidelines to Note

The FDA has released several guidelines for sunscreen manufacturers to ensure that their products are safe and effective.

  • The first guidance is for broad-spectrum sunscreens, which must protect against UVA and UVB rays.
  • The second guidance is for water-resistant sunscreens, which must maintain SPF levels after 40 or 80 minutes of water exposure.
  • The third guidance is for photo stabilization ingredients, which help prevent sunscreen ingredients' breakdown when exposed to light.
  • Lastly, the FDA has issued guidance on labeling sunscreens with an SPF of 15 or higher as "Broad Spectrum'' to indicate that they protect against both UVA and UVB rays. 

These FDA guidelines provide clarity to the industry and the public on various aspects of sunscreen safety and effectiveness. They address how to test sunscreen products for SPF and UVA protection, what claims can be made about sunscreen products, and what ingredients are considered safe and effective for use in sunscreens.

Some Potential Side Effects of Sunscreen

Sunscreen is an effective tool to protect your skin from the harmful effects of UV radiation. However, as with many other products, it can have some side effects. Here are a few:

  • Certain ingredients in sunscreen, such as oxybenzone, can disrupt hormones and cause allergic reactions. While most formulations are considered safe, some people experience allergic reactions or irritation. Allergic reactions may manifest as redness or rashes on the skin. In more severe cases, they may even lead to swelling or itchiness.
  • Some sunscreens contain chemicals that can be harmful to the environment if they enter the ocean through wastewater or runoff.
  • Meanwhile, phototoxic responses, also known as photosensitization, occur when a person's skin becomes more sensitive after prolonged exposure to UV light. It can result in burning or peeling, even in low sun conditions.

Because of these potential side effects, it is important to choose a high-quality sunscreen brand and always use it according to the directions on the label. By doing so, you can protect your skin from overexposure without compromising your health.

Sunblock vs. Sunscreen

Sunblock spray

Is sunblock just another name for sunscreen? Not really, but they’re typically all referred to as sunscreen.

Sunscreen usually refers to the chemical sunscreens mentioned above that protect against UVA rays. They use a chemical reaction to convert absorbed UV light to heat.

The mineral sunscreens or physical sunscreens we mentioned are usually the type of sunscreen referred to as sunblock. As the name suggests, they block UV rays by forming a physical shield instead of being absorbed by your skin.

You can usually tell the difference in the way that it looks on your skin. Sunblock usually forms a sort of white cast over the surface of your skin while sunscreen is absorbed into it.

Is one better than the other? Sunscreen protects against skin damage, while sunblock may be able to prevent skin damage and sunburn. Because sunscreen often has chemicals, people with sensitive skin may prefer using physical sunscreens or sunblock.

Making the right choice will depend on various factors, depending on your skin type and individual needs. Looking for the best sunscreen or sunblock for a particular skin type? Stay tuned for some of our favorite picks.

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Jordyn Wallerius, MS, RDN, CD

Reviewed by: Jordyn Wallerius, MS, RDN, CD

Jordyn has a bachelor’s degree in biology, a graduate degree in Human Nutrition and completed a dietetic internship at the Memphis VA. She's a dietitian at Nutrisense, and has experience working as a clinical dietitian at a VA medical center specializing in oncology and at the Mayo Clinic, working with a wide range of patients ranging from neonates in the NICU to adult ICU.

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