Sunscreen is one of the best tools to protect skin from the sun's UV rays. Prolonged sun exposure can lead to sunburn, wrinkles and, at worst, skin cancer.
While we know sunscreen is good for us, we might not excel at applying it or using it correctly.
One of the most misunderstood steps of proper sunscreen use is when to reapply. How often do you need to reapply if you're at the pool or beach all day? How about when you're sitting in your office? Let's look at how (and when!) to reapply sunscreen to keep skin healthy and sunburn-free.
Why reapplying sunscreen is important
While the best protection against UV rays is avoiding sun exposure altogether, it isn't really feasible, since both work and play can take us outside. We're also not immune to the sun when we're inside, especially if we enjoy natural light sitting near windows. And UV radiation is at its highest when most people are active — between 10 a.m. to 3 p.m.
Using sunscreen correctly throughout the day, even when indoors, helps reduce the lifetime risk of developing skin cancer. It can also help prevent some of the more cosmetic side effects of sun exposure, including wrinkles and age spots.
A brief SPF explainer, and why we have to reapply sunscreen
Unfortunately, applying sunscreen isn't a one-and-done process. That's because no sunscreen is able to provide you with all-day coverage. And how long you can wear sunscreen before reapplying it will be affected by the type of sunscreen you use (and how well you applied it the first time), your plans for the day and, most importantly, how the sun affects your particular skin.
How SPF is calculated?
First, it's important to know that there are two types of rays that pierce the earth's atmosphere: UVA and UVB rays. Each can cause different effects on the skin.
UVB rays have higher energy levels and can cause blistering sunburns in the short-term and skin cancers and melanomas in the long-term. UVA rays have lower energy levels and are associated with the immediate signs of sun exposure, including flushing and tanning. UVA rays, which are used in tanning beds, can cause premature aging such as wrinkles and age spots, and pierce through clouds and windows (including car windshields).
A common misunderstanding of sun protection factor, or SPF, is that the number stands for how much time you can be in the sun without burning. Allow us to bust that myth: According to the Federal Food and Drug Administration (FDA), SPF is a ratio of the amount of UVB rays needed to create a sunburn on skin protected with sunscreen relative to the amount of UVB rays needed to create a sunburn on skin without sunscreen.
So SPF measures the quantity of UV radiation, not the time you can be outside without getting burned. For example, an SPF 35 sunscreen will shield you from the sun until you've experienced 35 times more UVB rays than will cause your skin to redden without sunscreen. The higher the SPF number, the greater amount of UV light that is blocked. The American Academy of Dermatology recommends using a broad spectrum sunscreen of SPF 30 or higher. Broad spectrum means the product protects against both UVA and UVB rays.
Your sunscreen needs change day to day — as does your need to reapply
This can become confusing because several factors affect when someone's skin may start to burn. Everything from someone's skin type, how long they're outside, the time of day, their activity level, and how much sunscreen they applied in the first place can affect the amount of sun exposure, which will in turn affect the need to reapply.
"Each person is different," says Annie Christenson, a medial aesthetician with Houston Methodist. "Say that you have lighter skin, and you know that if you go in the sun, you can be out for maybe 15 minutes, and then you're going to start to feel it, whereas someone else may be able to go out for 30 minutes or more."
The intensity of UV rays changes throughout the day — you can expect more exposure during those UV power hours between 10 a.m. and 3 p.m. than during the early morning or evening hours.
For example, an early bird out for a walk at 7 a.m. may absorb the same amount of UV rays in an hour as a person out for a 15-minute walk at noon. And people with fair skin absorb more UV rays than those with darker skin under the same conditions. That's because melanin, a pigment in the outer layer of the skin, helps protect from UV rays naturally. But those with more melanin can still get sunburns and skin damage with too much exposure.
Your exposure levels will change day by day, too. If you're an office dweller Monday through Friday, your sunscreen needs are going to be very different during the week than when you spend the whole weekend at the pool.
As you are out and about and exposed to more UV rays, the active ingredients in sunscreen break down. This can be compounded by sweat or water during activity as well. Higher SPFs can give you more time before this breakdown occurs due to their strength, but no matter the level of SPF your sunscreen, you will have to reapply.
"You're not going to get eight hours of protection from any sunscreen," Christenson says.
When to reapply sunscreen
The general rule to reapply sunscreen is every two hours. But there is some leeway to this, according to Christenson.
"Being indoors, you don't really have to reapply," she says. "You're not sweating it off, you're not toweling it off after swimming. If you're sitting in front of your computer, and you're not close to any windows, you don't really have to reapply until you intend on leaving your office or home."
If you're near windows or skylights during the day, you'll want to consider reapplying every four to six hours. Christenson says leaving home or work should always prompt a reapplication, even if your activity will be brief, such as commuting in your car or taking your dog out for a walk.
Conversely, she says that if your day will be filled with outdoor activity, you'll want to reapply much earlier and often. To make sure your sunscreen will perform as it should, you may need to reapply as often as every 40 to 80 minutes.
"Sunscreen is not towel-proof or long-term sweat-proof," says Christenson. "So If you're on vacation, sitting on a beach, or you're in and out of the water and towel drying a lot, you'll need to reapply more often in those scenarios."
According to Christenson, using higher SPF sunscreens may give a feeling of over-confidence in these outdoor scenarios, which may lead people to stay out in the sun longer, or not reapply as often as they should.
How to reapply sunscreen
Whether you're using a mineral or chemical sunscreen, lotion or spray sunscreen or even a powder, the rules for reapplying are the same as applying that base layer. Make sure you're putting on the correct amount (which may be more than you think you need — read the instructions on your product) before you're exposed to the sun. Ideally, you're applying or reapplying your sunscreen 15 to 30 minutes before you head outside to give your skin enough time to absorb the product, according to Christenson.
How to reapply sunscreen over makeup
Whether you use a tinted moisturizer with SPF as your base makeup or do a full face every morning before leaving the house, one thing remains true: you'll need to reapply your sunscreen.
"If you've got makeup on, and you don't want to reapply cream sunscreen, there are really nice powder sunscreens that you can use to reapply on your face," Christenson said.
Powder sunscreens can be a loose or pressed powder or come formulated with a brush. They can give a matte finish over makeup, but as with any sunscreen, you won't receive the benefit of the reapplication if applied incorrectly. With powder, you may need more reapplications to make sure you get the full protection.
Tinted moisturizers, BB or CC creams and even makeup foundation are formulated with SPF these days. Christenson says the SPF in these products are an added benefit, but should not be used as your only sun protection.
"We may not apply our moisturizer or makeup as heavy as we need to get that sunscreen benefit, and we may not even put it on every day," Christenson says. "We should be wearing sunscreen every day. Plus, some of these products will only offer 15 to 30 SPF, which may not be enough for many people."
If you use these products, she recommends reapplying with a different sunscreen as needed instead of reaching for that tinted moisturizer again.
Add more to your sun protection arsenal
There are now several sun protection products that you can add to your routine in addition to sunscreen. Various brands offer sun protection clothing at various SPF levels, and you can find anything from T-shirts, leggings, gloves, scarves, sun hats and more.
"I do like the SPF clothing," Christenson says. "Wearing SPF gloves can help when you're driving in your commute, or if you're a person who has a lot of consistent exposure, shirts that cover your arms can be helpful."
Make it easier to reapply sunscreen
The best sunscreen is going to be the one you can use consistently. Getting an industrial-sized bottle of SPF 100 and committing to applying and reapplying it every day may be easier said than done, Christenson says. The true key to consistent use is finding products that work well on your skin — and most importantly, she says, feel good.
"You don't want something that feels sticky or uncomfortable on your face or body," Christenson says. "One sunscreen doesn't really do the trick anymore. Some sunscreens will feel better on your body, and some will work better and feel better on your face and neck."
To make it even easier to reapply sunscreen, Christenson says keeping smaller amounts of your favorite sunscreens in your pocket or bag for on-the-go application is your best bet.
"Keeping little tubes of sunscreen with you is handy because you can reapply on your hands after washing them, or reapply to your face and neck as needed," Christenson says. "Also, if you're wearing makeup, having a powder sunscreen with you to make that easier. You won't reapply if you don't have your products with you."
