Does sunscreen expire? Should you use it indoors? Everything you need to know to protect your skin this summer.

Sunscreen may smell like summer, but that doesn’t necessarily mean everyone applies it poolside, at the beach or before heading to the store for popsicles. Here’s why you should: While enjoying the warmer weather outside—or even just driving in your car or sitting near an office window – you are also being exposed to the sun’s harmful ultraviolet rays. These rays can damage the DNA of skin cells, which can cause skin cancer.

Skin cancer has been rising in the USA for years, with 1 in 5 people develop the disease by age 70, according to the Skin Cancer Foundation. But there is an easy and powerful tool that can help reduce this risk, while also preventing sunburn and protecting against premature skin aging. You guessed it – it’s sunscreen.

So what level of SPF should you use? How long does sunscreen last? And does makeup with SPF count as sun protection? Yahoo Life asked dermatologists these common questions and more. Here’s everything you need to know about sunscreen and how to better protect your skin this summer and beyond.

What does SPF mean – and which one should you use?

FPS, or sun protection factor, measures how well sunscreen protects against sunburn, according to the American Academy of Dermatology (AAD). So how are different FPS levels measured? According to MD Anderson Cancer Center, an SPF 15 sunscreen blocks 93% of the sun’s harmful UVB rays and SPF 30 blocks 97%. Once you get past this, you will only receive a small increase in protection. For example, SPF 50 blocks 98% of UVB rays, while SPF 100 blocks 99% of them. No sunscreen offers 100% protection against harmful UV rays.

The AAD recommends using a broad spectrum sunscreen – which means it protects against UVA rays (which prematurely age the skin) and UVB rays (which cause sunburn) – with SPF 30 or higher. “Above that can be helpful, but really deep protection against cancer starts at SPF 30,” Dr Daniel Butlerdermatologist in Tucson, Arizona, told Yahoo Life.

What is the difference between mineral and chemical sunscreen?

The main differences are the ingredients and the way they protect against the sun’s rays. “Chemical sunscreens,” such as avobenzone, oxybenzone and octinoxate, “absorb UV rays, while mineral sunscreens – zinc oxide or titanium dioxide – act as a physical barrier that prevents UV rays from reaching the skin.” Dr., dermatologist at Schweiger Dermatology Group in Freehold, NJ, tells Yahoo Life. “Both offer good protection.”

However, chemical sunscreens generate some controversy and can cause allergic reactions in some people. “There is a greater chance of irritation and burning due to the combination of multiple ingredients in order to provide UVA and UVB protection,” Dr. Cula Svidzinskicosmetic dermatologist at Sadick Dermatology in New York City, he told Yahoo Life. Mineral (aka physical) sunscreens, on the other hand, are naturally broad-spectrum, blocking UVA and UVB rays as well as blue light, says Svidzinski. While these sunscreens can leave a white cast—the minerals themselves are white and sit on top of the skin—the formulations have come a long way.

Where and when should you use sunscreen?

Experts say sunscreen should be a daily habit. “I recommend that people use sunscreen daily in the morning and then reapply if they are deliberately exposed to the sun,” says Butler. But it’s important to note that even on cloudy days, you’re still exposed to some harmful UV rays. That’s why Dr.assistant professor of dermatology at Baylor College of Medicine, told Yahoo Life that sunscreen should be used “even on cold or cloudy days” and “especially near reflective surfaces such as water, snow or sand.”

Even if you’re indoors, it’s still a good idea to wear sunscreen as UV rays, specifically UVA, can penetrate windows, Dr. Marisa Garshick, a dermatologist in New York City and Englewood, NJ, tells Yahoo Life. “It is also important to note that blue light can be emitted from computer and phone screens and can contribute to changes in the skin, and using sunscreen can help protect the skin,” she says.

Butler agrees, adding, “Although indoor light and computer light are unlikely to cause cancerous changes, photoaging can still occur indoors or in front of a computer screen. Therefore, I recommend using sunscreen on your face if you are indoors or in front of a computer for long periods of time.

How much sunscreen should you put on?

“To reach the SPF indicated on the label, you need about a cup of sunscreen—most people tend to use less,” says Miller.

Ren adds that sunscreen should also be applied 15 minutes before leaving the house. And remember to spread it on commonly overlooked areas, like the backs of your ears, the backs of your hands, and the tops of your feet, as well as using lip balm with SPF 30 or higher. As an expert put: “Lip gloss that doesn’t contain SPF is like applying baby oil to your lips.”

How long does sun protection last?

In general, sunscreen lasts about two hours. If you are cool and dry indoors and are not near any windows, you can stretch this to four to six hoursaccording to the Skin Cancer Foundation.

But sunscreen should be reapplied every two hours if you’re outdoors, and more often if you’re swimming or sweating. Water-resistant sunscreens can protect your skin, even when wet, for a maximum of 40-80 minutes and then need to be reapplied. (There is no such thing as waterproof or sweatproof sunscreen, so manufacturers are not allowed to make these claims, according to the Food and Drug Administration.)

“Even if you opt for a high SPF sunscreen, you won’t be reaping the full benefits of that high SPF sunscreen unless you completely cover sun-exposed areas and reapply,” says Ren.

Does sunscreen expire?

Sunscreen doesn’t last forever, so it’s worth checking your cupboards and beach bags for expired products. FDA Regulations require all medications without a prescription, including sunscreen, has an expiration date, although there is an exception to this rule if the manufacturer’s stability testing shows that the product will remain stable for at least three years. Therefore, any sunscreen without an expiration date should be considered expired after three years have passed since you purchased it.

“Many sunscreens include an expiration date,” says Svidzinski. “If your sunscreen doesn’t have an expiration date, write the date you purchased it on the bottle and discard it three years later.” Not sure how old your sunscreen is? Throw it away, according to the FDA.

Avoid leaving sunscreen in hot cars or in direct sunlight, which Garshick says can affect its effectiveness. “Leaving sunscreen in a hot car can break down the preservatives, which can lead to colonization by bacteria or yeast,” explains Butler. You should also keep an eye out for changes in the color, smell, or consistency of your sunscreen. “Signs that should make you throw it away are if it smells bad or if it’s too watery when it comes out,” he says.

How to choose the right sunscreen for you

The most important factor in choosing the “right” sunscreen is selecting the recommended SPF 30, says Svidzinski. “After that, the ‘right sunscreen’ is the one you’re going to use,” she says. Butler tells her patients to try three or four different options before deciding on a daily sunscreen that suits them.

For those with sensitive skin, Garshick says it’s best to opt for a mineral sunscreen “as they tend to be less irritating and less likely to cause an allergic reaction.” Those with acne-prone skin “should look for noncomedogenic or oil-free sunscreens to help minimize any potential for breakouts,” she says.

For those with darker skin, Garshick says chemical sunscreens may be preferred “as they tend to absorb easily without leaving a white cast.” However, Svidzinski says that with the improved formulation of mineral sunscreens “there are many more options for dark skin.”

Garshick adds that tinted sunscreens are also an option to better match a specific skin tone.

Lotions, sticks and sprays: do they all offer the same protection?

“Sunscreen sprays and sticks can offer the same amount of protection as lotions if an adequate amount is applied,” says Garshick. “The problem with most sprays and sticks is that people typically don’t apply enough or don’t apply an even layer, so there are areas that can be at risk for burns. Sun protection sprays aren’t bad for you, but it’s important to use them correctly. Ultimately, some sunscreen is better than no sunscreen, but either way it is important to ensure that enough sunscreen is applied.

However, some dermatologists recommend caution when using spray sunscreen. “Sprays are popular because of their ease of use, but little is known about the effects of inhaling sunscreen particles on the lungs, making it difficult to recommend their use,” says Miller. Butler adds that “in relation to spray sunscreens, if aerosolized, they may contain benzenes which, at high levels, can cause negative impacts on health”.

But if you’re determined to use them, Svidzinski says it’s “essential to apply spray sunscreen to ensure even coverage.” And since there is some concern about inhalation, she recommends applying them in a well-ventilated area and avoiding spraying them directly on the face.

Is your daily moisturizer or foundation with SPF enough?

Dermatologists are confused about whether makeup and facial moisturizers with SPF offer enough sun protection. (Also worth noting: They only help protect your face — any other exposed skin needs sunscreen, too.)

“They’re great for daily sun protection,” says Butler. “Ideally, they would have SPF 30 or higher to ensure the impact on cancer protection, as well as the benefits of preventing aging.”

However, Garshick says that even though a daily moisturizer or foundation with SPF may indicate that it provides sun protection, “it’s typically not considered sufficient because most of the time people don’t apply enough moisturizer or foundation to get the right amount of protection.” necessary. indicated on the label.”

Svidzinski agrees. “Makeup with SPF is not a substitute for a stand-alone sunscreen,” she says. “Daily moisturizer with a minimum SPF of 30 may be appropriate if your day consists of very little time outdoors.” But, she says, in addition to not applying enough to provide full protection, you probably won’t be reapplying makeup or moisturizer with SPF throughout the day. “That’s why I recommend using a specific SPF 30 physical sunscreen in addition to your moisturizer or makeup with SPF.”

What else can you do to protect yourself from the sun?

While sunscreen typically gets the most attention, it’s not the only way to avoid harmful UV rays. There are other measures you can and should take, experts say — namely, seeking shade when the sun’s rays are strongest. Typically this occurs between 10am and 2pm. “But of course this can vary depending on your location,” says Ren, “so most importantly, seek shade whenever your shadow is shorter than you.” Additionally, wear sun-protective clothing. This includes tightly woven long-sleeved shirts and pants with Ultraviolet Protection Factorwide-brimmed hats and large-framed sunglasses with UV protection, says Ren.