Sunscreen SPF Ratings, Types Explained 

Choosing the best sunscreen for you can feel daunting. Various ingredients, sunscreen types and SPF levels can make the decision challenging, but routinely using proper sun protection could make the difference in whether you develop skin cancer or other skin conditions like melasma or dark spots later.

"Sun protection starts with awareness," said Theodore Seger, MD, a primary care doctor with Franciscan Physician Network Downtown Indy. "It's important that you apply sunscreen to all sun exposed areas every two hours, and you'll need to reapply sometimes more frequently, such as if you've been sweating a lot that day."

Why Is Sunscreen Important?

Sunscreen can play an essential role in skin care, regardless of age. Sunscreen use helps prevent sunburn, skin cancer and premature skin aging, including wrinkles and age spots.

It’s tempting on cloudy Indiana days to avoid using sunscreen. But even on overcast days, as much as 80% of UV rays can penetrate your skin, the American Academy of Dermatology says to protect your skin and reduce your risk of skin cancer and skin damage, you should apply sunscreen every time you are outside, even on cloudy days.

Even if you have darker skin or don't burn easily, sunscreen use is essential. Melanin, the dark pigment in skin, provides some protection against the sun’s harmful rays, but not as much as people tend to think. The darker your skin tone, the higher your risk that UV rays and visible light from the sun will cause dark spots, also known as hyperpigmentation, on your skin.

What Should I Look For In A Sunscreen?

The American Academy of Dermatology recommends looking for three things when shopping for sunscreen:

• SPF 30 (or higher)
• UVA/UVB, or broad-spectrum, protection
• Water resistance

What Does SPF Mean?

We have all heard of SPF. But what does it really mean? Why is it so important?

SPF is an acronym for Sun Protection Factor. It is a way of determining how long a product will help prevent damage from UV rays, primarily UVB rays. These rays are shorter and stronger and are the reason behind most sunburns. This does not mean we don't need to worry about UVA rays, though. They are responsible for issues deeper in the skin, including aging and wrinkles.

When choosing the SPF, know that the higher the number, the longer the protection should last. SPF tells us how long it would take to burn if you wore sun protection compared to not wearing sunscreen. With SPF 30, for example, it should take 30 times longer to burn than if you weren’t wearing sunscreen. But there’s more to it than that.

The SPF rating assumes you are following the product's instructions for proper use and the need for reapplication. This includes:

• Putting on the sunscreen at least 30 minutes before sun exposure.
• Being liberal with your application. (Think of filling a shot glass when it comes to how much sunscreen should be used.)
• Reapplying sunscreen after sweating, water sports, etc.

What SPF Should I Use?

The Skin Cancer Foundation and the American Academy of Dermatology recommend wearing a water-resistant, broad-spectrum sunscreen with a minimum of SPF 30, which blocks 97 percent of the sun's UVB rays, for outdoor activities.

Sunscreen with an SPF of 30 allows 3% of rays through. A higher protection number, SPF 50, allows 2% of rays through.

Many factors come into play when it comes to the sun and SPF. Your genetic makeup could potentially place you at a higher risk for skin cancer than your neighbor. Also, any medications you take or apply can alter your protection from the sun. Lastly, not using enough sunscreen, applying the product unevenly, or even forgetting to reapply will play a role in protecting you from the sun’s harmful UV rays.

Is A Higher SPF Better?

Once you break down how much protection you are getting from the extremely high SPF's and compare what is in them to something slightly less in strength, you may find that you aren't getting that much more protection. Using an SPF of 50 for higher elevations or extended periods in the sun would be wise, but the SPF of 100 isn't going to make any promises of better protection.

Some people mistakenly think they must apply sunscreen just once daily if it has a high SPF rating. However, the SPF rating doesn't indicate how long you can stay in the sun or how often you should apply your sunscreen. It's simply a rating of the sunscreen's effectiveness in protecting the skin from UV light.

What Is Broad-Spectrum Coverage?

Regardless of the sunscreen type, look for “broad-spectrum” coverage. Broad-spectrum means it protects against the two main types of UV light that contribute to skin cancer risk: ultraviolet A (UVA) and ultraviolet B (UVB).

All sunscreens protect against UVB rays, the leading cause of sunburn and skin cancers. Broad-spectrum SPF also protects against UVA rays, which are associated with skin aging.

Why Is Water-Resistant Sunscreen Important?

There is no such thing as waterproof sunscreen, but sunscreen can be water-resistant for a time. Water-resistant sunscreen only lasts 40 to 80 minutes on wet skin, so plan to reapply it after spending time in the water or sweating heavily.

What Form Of Sunscreen Should I Use?

Whether you choose lotion, spray or stick, select the form you are more likely to use and reapply.

If that’s lotion, the Skin Cancer Foundation recommends applying at least 1 ounce, which is also two tablespoons or the amount that fills a shot glass.

For spray, keep applying until your skin glistens. The bottle may say “no rub,” but smoothing it into your skin will ensure even coverage. Avoid using aerosol sprays on or near your face because they contain ingredients that, when inhaled deeply, may cause irritation and damage your lungs.

It may be better to avoid spray for young children, but you can also spray it onto your hands and rub it onto your face or your child.

Stick sunscreen is great for small areas like the face and ears. Make four passes with the sunscreen over each area you’re protecting. Rub the sunscreen afterward for even coverage.

Even with this protection, seek shade and wear protective clothing whenever possible.

Should I Choose A Mineral Sunscreen Or A Chemical Sunscreen?

The two main choices for sunscreen are mineral sunscreens and chemical sunscreens. Each has benefits, but depending on your skin type and lifestyle, one may be more favorable.

Mineral Sunscreens 

Mineral sunscreen sits on the skin’s surface. It physically blocks ultraviolet (UV) light before those rays penetrate the skin.

While offering instant protection, it can be harder to rub in, needs to be applied more frequently and tends to leave a white film on the skin. Yet, it’s also gentler than chemical sunblock, potentially making it a good choice for sensitive skin. Mineral sunscreen often contains titanium dioxide and zinc oxide, which the U.S. Food and Drug Administration recognizes as safe and effective.

Chemical Sunscreens

Chemical sunscreens allow UV light to penetrate skin, after which the chemicals convert the UV light into heat. This is released from the skin.

The downsides are that chemical sunscreens need to be applied at least 20 minutes before sun exposure and that there are concerns about the ingredients in them, especially oxybenzone.

Some of the ingredients in these sunscreens may cause environmental issues, including damage to coral reefs. They may also pose health risks like hormone disruption and allergic skin reactions. The FDA is waiting for more safety data before labeling them as safe and effective.

Yet, chemical sunscreen is also easy to rub in and leaves less residue on the skin.

Experts say the health risks of sun exposure far outweigh the potential risk of absorbing sunscreen chemicals.

The American Academy of Dermatology has more on choosing the right sunscreen for your skin.

Ultimately, the best sunscreen is one you'll wear often, as the sun emits UV rays year-round.

HealthDay News contributed information to this article.