How Often Should You Be Reapplying Sunscreen, According to Dermatologists
May 30, 2021
Putting on SPF sunscreen once a may not be enough
It is the second day of your vacation on the beach and you notice a tenderness on your skin. Hot and painful, there is one thing this can mean. You are sunburned. You put on sunscreen but forgot to reapply it.
This can happen to the best and most diligent people. Forgetting to reapply sunscreen can be a problem. This can lead to a more uncomfortable skin rash. According to the Skin Cancer Foundation, melanoma is the deadliest form of skin cancer, and having five or more sunburns can double your risk.
Using sunscreen and well as putting on sun-safe clothing, is the best way to reduce the risk of sunburn and skin cancer. Sunscreen that has at least SPF 15 used every day can reduce your risk of developing cancerous cells. Risks for squamous cell carcinoma are reduced approximately 40% and melanoma 50%. Outdoors, you should apply at least SPF 30.
Putting on sunscreen once is important, and dermatologists advise to reapply it again and make it a habit.
Sunscreen works, but how?
Two types of sunscreen work differently through either physical or chemical blockers. Mineral-type sunscreens have ingredients such as titanium dioxide and zinc oxide. These sit as a physical barrier on the skin that prevents the ultraviolet rays from penetrating the skin. Chemical sunscreen absorbs the UV rays before they harm your skin and have Ingredients such as avobenzone and octisalate to do their job against the harmful UV rays. Less likely to be a cause of skin irritation are the physical sunscreens, but according to the Skin Cancer Foundation, both types are safe and effective.
A way to understand how sunscreen works are to think of it like a cup. Heather Woolery-Lloyd, M.D. is a board-certified dermatologist and director of Ethnic Skin Care at the University of Miami Department of Dermatology uses the comparison to a cup that gets filled by the sun’s rays. The cup will get full after a few hours. At this point, it can’t absorb more rays or continue to protect your skin. According to Dr. Woolery-Lloyd, “Reapplying sunscreen is like putting out a fresh cup to absorb the sun’s rays, rather than letting it get into your skin.”
How often should sunscreen be reapplied?
Depending on your activities for the day, you may need to reapply sunscreen more often. Swimming and sweat can reduce the time you would be protected from the sun’s rays. Dr. Woolery-Lloyd says to be protected from harmful rays all day, you would need to reapply every two hours.
Be liberal and slather it on. Don’t be afraid to apply enough sunblock during the first application. If people do not apply enough sunscreen, they aren’t getting the level of protection that is being stated on the label. Leslie Baumann, M.D. is a board-certified dermatologist, researcher, and founder of Baumann Cosmetic Dermatology. She notes that “This makes the sunscreen less effective, causing it to lose its ability to protect the skin.”
Is it safe to skip using sunscreen when it is cloudy outside or feels cold? Even on a cloudy day, ultraviolet light including the UVB rays that damage your skin is still there. The UVB may be less present, but Dr. Baumann says UVA rays remain strong and cause more skin damage. During activities in cold weather such as skiing, or on rainy days, you still need to wear sunscreen.
When should sunblock be applied more frequently?
A general rule of thumb, reapply sunblock every two hours to remain protected from the sun’s harmful rays.
As a general rule, reapplying sunscreen every two hours will protect you from the sun’s harmful rays. But there are a few situations where you may want to reapply more often: There are situations where you might want to reapply the sunscreen more often:
When you are in a vehicle driving or as a passenger
Drivers and passengers have a good chance of being in direct sunlight. Dr. Woolery-Lloyd says “People underestimate how much sun exposure they get when they’re in the car.” and tells her patients to be extra careful during long commutes and to stick with the rule of applying every two hours.
When you are swimming or when water may wash it away
Even the water-resistant sunscreens still should be reapplied every two hours. Also, each time using a towel, you should then reapply sunscreen. When the water is wiped away from your skin, so also is your sunscreen and protection.
When you are near a window
Windows allow for the sun’s rays to reach you, whether they are open or closed. Just because you are indoors, it does not make you safe from the sun’s rays. Dr. Woolery-Lloydmakes note that “If your office has a window, you can bet that you’re actually getting quite a bit of sun.” If you are sitting by a window for a long period of time, once again follow the rule of reapplying every two hours or more.
How to remember to reapply sunscreen
There are things you can do to help remember using sunscreen and not forget when it’s time to reapply. Because it is easy to forget, work on adding it to a routine and get it in your daily habits. Dr. Baumann suggests to “Apply sunscreen in the morning after you brush your teeth, then apply it again before you go to lunch or anytime you are headed outside.” Also, do not forget important areas such as the ears, front and back of the neck, chest, and the top of your hands.
Find a sunscreen formula that you love and you will be more likely to remember it. If it is a sunscreen that you love, perhaps one especially for the face, it will become part of your daily routine. For the face, there are sunscreens for use with makeup. Powder sunscreens can easily be reapplied over. Also, tinted sunscreens offer a lighter coverage, and moisturizers with SPF if you prefer to go bare-faced.
Apps on your phone can also remind you to use and reapply sunscreen. Two examples are QSun and My Skin Track UV. Dr. Woolery-Lloyd says “These apps are great for not only tracking how much sun exposure you’re getting but also for telling you when you need to reapply sunscreen. These apps can help you have a fun and safe day in the sun.