Sunscreen is usually associated with the summer. It’s commonly known as that thick, chalky liquid you slather on before a beach trip or that oily mist you spray on your skin that stings if it gets too close to your eyes. It reeks of that distinctive sunscreen smell and gets sticky if you sweat even the tiniest bit. However, that gross, uncomfortable sunscreen experience is only a tiny peek into the world of SPF. It’s an ever-advancing technology that has come miles since that opaque white substance lifeguards caked on their noses. Sunscreen can be weightless and virtually undetectable and isn’t just for wearing in the summer or even on sunny days.

Got questions? We don’t blame you. We asked Dr. Yoram Harth, Board-Certified dermatologist and Medical Director of MDacne and Giedre Whitworth, licensed esthetician and owner of In The Glow beauty bar to clear up some frequently asked questions about sunscreen.

When should you wear sunscreen?

In short, sunscreen should be worn every single day, whether it’s hot or cold, sunny or cloudy, and whether you’re spending the day inside or outside. Why? UV radiation.

The UV radiation is produced by the sun. There are three classifications of UV light: UVA, UVB, and UVC. UVC is the shortest of the rays and they are absorbed into the ozone layer before they reach us. UVA (aging) rays and UVB (burning) rays do,” explains Giedre Whitworth, licensed esthetician and owner of In the Glow beauty bar. “No matter what type of weather or temperature is outside, the harmful rays still penetrate through atmosphere and they impact the skin. UVA are the longest rays and that allows them to penetrate through clouds, windows and into the dermis(the deepest layer of our skin). UVB rays are shorter and cloudy weather conditions do filter them out some but enough still reach us and penetrate into the skin.

The dangers of UV exposure aren’t just cosmetic— sunburns and accelerated aging only scratch the surface of the effects of spending too much unprotected time in the sun.

“UV exposure can suppress the immune system and increase the risk of skin cancer,” warns Whitworth. “When looking for a good sunscreen, one must look for a broad spectrum sunscreen to block both types of these rays. UV rays are the most intense between 10 am and 3 pm because of the way the sun is positioned in relation to earth during that time”— so make sure you have sufficient sun protection during those hours.

Do people with darker skin tones still need to wear sunscreen?

Absolutely! Though people with deep skin tones do produce more melanin and have more protection against UV rays, they are still not immune to skin cancer and other adverse effects of UV exposure.

“Melanin has the ability to cover the DNA of the skin cells thus shielding it from damage. Damaged DNA of the skin may result in skin cancer, aging... Essentially, darker skin tones do have more protection from the sun due to a higher quantity of melanin (which hovers over the DNA of the skin, protecting it from damage) but it is still not enough of it to protect from damaging effects of the rays completely. That is why everyone should wear sunscreen,” concludes Whitworth.

What is SPF? What SPF level should I buy?

According to Dr. Yoram Harth, “SPF (Sun Protective Factor) is the number used to measure the protective power of the sunscreen.”

You might think a sunscreen with SPF 60 is twice as powerful as a sunscreen with SPF 30, but Dr. Harth says that is not the case.

“Sunscreen manufacturers want us to buy sunscreens with ultra-high SPF (50, 60 and even 100) and pay a premium price for these products,” she says. “Interestingly, a sunscreen with SPF 60 will NOT block twice the UV than a sunscreen with SPF 30. A sunscreen with SPF 60 block[s] 100-100/60 = 98.4% of the UV. A sunscreen with SPF 30 blocks 100-100/30 = 96.7% of the UV. The difference is negligible = 1.7% Moreover, the high [concentration] of sun screening chemicals in high SPF sunscreens increases the risk of skin irritation and allergies.” Though that SPF 100 sunscreen may seem like it offers optimal protection, it is simply not worth the price to buy such a high SPF.

So which SPF will give you the most bang for your buck?

“The optimal sunscreen would have SPF 30,” says Dr. Harth. “Thus, sunscreen with SPFs higher than 30 are not worth the money and should [usually be avoided].”

Also, look for sunscreen that is broad spectrum (protects against both UVB and UVA) and water resistant, especially if you’re planning on swimming or exercising. “The label water resistant means that the sunscreen was tested to stay on the skin for at least 80 minutes after swimming,” explains Dr. Harth. “The bonus of such sunscreens is that they are also sweat resistant and will remain active longer on your skin even in the warmest climate.”

What is the difference between chemical and physical sunscreen?

According to Geidre Whitworth, “Chemical sunscreens work in the skin by neutralizing the rays once they come in contact with them. The easiest way to think of mineral sunscreen is to picture them like little mirrors that sit on top of the skin and deflect the rays without allowing them to penetrate the skin.” However, “[t]he issue with chemical sunscreens is that the ingredients in them do protect from sun damage but the ingredients themselves can create free radical damage that results in a similar outcome as UV damage itself.”

To counter the negative effects of chemical sunscreen, Whitworth says, “[it’s] best to use one that has antioxidants added to it, or apply antioxidants prior to applying sunscreen. Antioxidant names to look for are green tea extracts, vitamin C, thiotaine, vitamin E, etc. In general, using antioxidants daily(no matter [which] SPF, mineral or chemical) allow for constant repair of UV ray damaged cells, thus making sun protection that much more effective.”

Physical sunscreens, on the other hand, are “based on zinc oxide and titanium oxide,” according to Dr. Harth. Unfortunately, they also have their share of negatives— their active ingredients are more likely to clog your pores, especially if you have acne-prone skin.

How much sunscreen should you apply, and when should you apply it?

“For the face,” Dr. Hearth says, “a nickel size of sunscreen is enough. Most adults need about 1 ounce — or enough to fill a shot glass — to fully cover their body. Sunscreen should be applied every 3 hours when outdoors. For women that use makeup, once a day application in the morning is enough.”

What additional ingredients should I look for or avoid in a sunscreen?

Though a sunscreen’s active ingredients determine its level of UV protection, its inactive ingredients are just as important. Some sunscreens contain additional chemicals that could be harmful to your skin.

“One ingredient that should be avoided,” Dr. Hearth warns, “is the preservative methylisothiazolinone, a frequent skin sensitizer. Methylisothiazolinone is used alone or in combination with another preservative called methylchloroisothiazolinone.” Though it was deemed unsafe and banned in Europe, it is still present in some US-manufactured sunscreens.

“Some of the inactive ingredients are beneficial for a specific group of people,” Dr. Hearth adds. “People with acne or acne-prone skin, for example, should look for an oil-free sunscreen that contains acne safe inactive ingredients.”

“Some of these sunscreens also include plant-based ingredients that reduce skin redness, moisturize the skin and help fade brown spots. Examples for these ingredients are Aloe Vera leaf extract [which] is a potent antioxidant [or] green tea extract that helps lighten pigmentation, even[s] skin tone, and boost[s] skin's natural healing.”

Best Sunscreen Recommendations

It’s tough to find a body sunscreen that isn’t too sticky or greasy, and even harder to find a face sunscreen that’s oil-free and doesn’t leave a white cast. But don’t worry— we’ve selected four face and body sunscreens that are so weightless, they feel like a second skin.

Supergoop! Unseen Sunscreen Broad Spectrum SPF 40

$32 at the time of publication

This face sunscreen from Supergoop! is oil-free, loaded with antioxidants, and perfect for any skin type. It provides broad spectrum protection against UVA and UVB rays but also includes red algae, an ingredient that blocks blue light, the light that comes from your phone and other screens. It’s an Allure Best of Beauty winner and is specially formulated to provide a gripping base beneath your makeup.

Buy this sunscreen at sephora.com.

Shiseido Urban Environment Oil-Free UV Protector Broad Spectrum Face Sunscreen SPF 42

$35 at the time of publication

This Shiseido sunscreen is so light, you’ll forget you even put it on your face! Oil-free and mattifying, this sunscreen is perfect for people with oily or combination skin. It also contains antioxidant-rich ingredients that defend against pollution and free radicals— ideal for those who live in an urban environment.

Buy this sunscreen at sephora.com.

Sun Bum Original SPF 50 Sunscreen Spray

$16 at the time of publication

Say goodbye to that greasy sunscreen spray that stinks of chemicals! This sunscreen spray from Sun Bum is ultra-sheer, fortified with vitamin E, and dry-touch. It’s also water resistant, so it’s perfect for throwing in your beach bag for a trip to the shore!

Buy this sunscreen at urbanoutfitters.com.

Glossier Invisible Shield Daily Sunscreen SPF 35

$25 at the time of publication

Glossier calls this weightless sunscreen the “sunscreen for people who hate wearing sunscreen.” It has a water-gel formula, so it melts into the skin when applied and leaves absolutely no white cast. It even includes the smallest dash of sweet orange peel oil for a deliciously summery scent!

Buy this sunscreen at glossier.com.