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Common Skin Questions: Solved

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woman wearing broad-brimmed hat and sunglasses

Everyone wants a youthful, glowing complexion, but when it comes to protecting yourself from harmful UV rays, it can sometimes be hard to separate fact from fiction.

Can you get sunburned through a car window? What about burn on a cloudy day? Cooper Clinic Preventive and Cosmetic Dermatologist Kejal Shah, MD, FAAD, answers some burning questions regarding skin care.


What’s the difference between UVA and UVB?

UVA is a longer wavelength then UVB, but both play a role in premature skin aging and skin cancers.

Shah says when you think about UVA, think about aging. UVA rays penetrate deep into the dermis, the skin’s thickest layer. Unprotected exposure can lead to premature skin aging and wrinkling, also known as photoaging.

When you think of UVB, think of “burn.” UVB rays burn the superficial layers of your skin. 

Excessive UV radiation can damage skin’s cellular DNA and lead to skin cancer such as basal cell carcinoma, squamous cell carcinoma as well as melanoma.

What SPF sunscreen should you buy?

Store shelves are now lined with sunscreen bottles with SPF ranges from less than 8 all the way up to 100. What does it all mean?

Sun Protective Factor (SPF) is a way to measure the sunscreen’s efficacy. “Take a bottle of SPF 15 for example,” explains Shah. “That means it takes about 15 times longer for someone to get sunburned while wearing it compared to someone not wearing sunscreen at all.”

Shah says sunscreen with SPF 15 protects your skin up to 94 percent against UVB rays, SPF 30 protects up to 97 percent and SPF 50 protects up to 98 percent against UVB rays.  

When shopping for sunscreen, Shah recommends broad-spectrum sunscreen SPF 30 or greater, ideally containing zinc or titanium.

Is sunscreen enough to protect your skin?

Sunscreen is just one of many tools to protect your skin against skin cancer and premature photoaging, but it's important to use it correctly.

“You should choose a broad-spectrum sunscreen with SPF 30 or greater,” says Shah. "Use about one ounce of sunscreen, which is about the size of your palm, to cover your face, chest and arms. Do this 30 minutes before going outside. It's also important to reapply your sunscreen every two hours if you're out in the sun for an extended period of time."

In addition to sunscreen, seek shade and wear a broad-brimmed hat for additional sun protection.

Is sunscreen in your cosmetics enough?

No. Cosmetic products may contain sunscreen, but may not have the recommended amount of SPF.

“I recommend my patients wear a sunscreen underneath their makeup and reapply sunscreen if they are going to be out in the sun,” says Shah.

Can you burn on a cloudy day?

Yes. UV rays can penetrate through clouds and cause sunburn. It's important to always wear sunscreen, even when it's cloudy.

Are individuals with dark skin at risk of getting skin cancer?

While lighter skin types burn more easily, Shah says no skin type is immune from developing skin cancer. 

Individuals with darker skin have more melanin, a pigment that protects skin against harmful UV radiation, but that doesn't protect them completely. They're still at risk for developing skin cancer.

“If those with darker skin get skin cancer such as melanoma, often they are the more dangerous types and in locations not exposed to sun, such as their palms and soles of the feet," says Shah. "This is called acral lentiginous melanoma. Skin cancer is not only caused from UV radiation, but other factors such as genetics and environmental factors."   

What about your vitamin D?

You can use the excuse that you’re “laying out to get your vitamin D” all you want, but Shah says it’s not necessary.

“Depending on where you live, your daily exposure to sun is usually enough to get your recommended daily value of vitamin D,” says Shah. “You don’t need to be out in the sun during peak UV times to get your vitamin D level up.”

If you’re vitamin D deficient, Shah says there are healthier options to boost your level, such as taking a vitamin D supplement or consuming food fortified with vitamin D.

Is a tanning bed better than the sun?

Absolutely not. 

UV radiation, whether from the sun or from a tanning bed, is a carcinogen. The light used in tanning beds is UVA, which penetrates the skin deeper and causes skin cancer and photoaging.

Going in a tanning bed increases your risk of developing squamous cell carcinoma by 70 percent and basal cell carcinoma by 30 percent. People who first use a tanning bed before age 35 increase their risk of melanoma by 75 percent.

Shah says self-tanning products are a great option if you’re looking to get tanned skin, but they don’t protect the skin from UV rays. Sunscreen still needs to be applied when you’re outside. 

Can you get sunburned through a car window?

Surprisingly, yes! 

Glass reduces but doesn’t completely block the penetration of UV radiation. UVA rays penetrate more through the glass than UVB,  increasing the risk of skin cancer as well as photoaging. This is especially true if you spend a lot of time driving without sunscreen.

“Consider adding tinted UV-protective film to your car windows as well as house and work windows," says Shah. "Make sure you wear sunscreen all the time.” 

When it comes to skin cancer, prevention is key. Shah recommends getting a thorough, full-body skin cancer screening, such as the one offered at Cooper Clinic Dermatology, every year. It’s also important to do a self-check at home every month. 

For more information or to schedule a comprehensive skin exam at Cooper Clinic Dermatology, visit or call 972.367.6000.