Does SPF 50 mean 50 minutes?
“The SPF gives you an idea of how long you can be in the sun before you burn,” adds Peterson Pierre M.D., board-certified dermatologist at the Pierre Skin Care Institute. “For instance, if you're super sensitive and you burn in one minute, a SPF 50 will give you 50 minutes before you burn.”
SPF50 should protect you 50 times as long as your skin would be able to naturally protect itself. However, remember that the lower the SPF and longer the length of time since application, the less UVB rays will be filtered, so a reapplication every two hours is highly recommended.
So sunscreen with an SPF of 50 means that when used on the skin, it can protect the skin against the harmful effects of UVB rays for about 500 minutes and has the ability to block the penetration of UVB rays into the body. up to 98%.
"Imagine that your skin normally begins to burn after 10 minutes in full sun without any protection. A 30 SPF sunscreen would provide 30 times the protection of no sunscreen." That means 30 times longer before you start to burn, or in this case, 300 minutes.
Sun Protection Factor (SPF) is a measure of protection sunscreen gives against UVB radiation. The rating tells you how long the sun's UV would take to redden your skin compared with using no sunscreen. For example, in theory SPF50 would take you 50 times longer to burn than if you use no sunscreen.
Generally, sunscreen should be reapplied every two hours, especially after swimming or sweating. If you work indoors and sit away from windows, you may not need a second application. Be mindful of how often you step outside, though. Keep a spare bottle of sunscreen at your desk just to be safe.
The answer to this varies depending on you, your skin, and how much time you'll be spending in the sun. The Skin Cancer Foundation recommends choosing a sunscreen that's in the SPF 15-50 range. SPF 15 is best for those who spend most of their time indoors or will spend a short amount of time in the sun.
If, for example, a person develops redness after 5 minutes of exposure without sun protection, the application of an SPF 50 sun cream multiplied by 50 the time of exposure before getting a sunburn (5 minutes * 50 = 250 minutes).
No, but this myth continues to prevail. When you look at the science, sunscreens allow people to stay out in the sun longer and protect against the UV rays that can cause skin cancer, but they do not prevent the skin from developing a tan.
Yes, you read that right! Even formulas as strong as SPF 50 don't block all ultraviolet rays, which are the ones that color your skin a nice, even bronze. That means you can get a bronze tan while ensuring you don't burn and try to avoid skin cancer at the same time.
Why avoid SPF?
High SPF products require higher concentrations of sun-filtering chemicals than low SPF sunscreens do. Some of these ingredients may pose health risks when they penetrate the skin and have been linked to tissue damage and potential hormone disruption. Some may trigger allergic skin reactions.
What Does the SPF Number Mean? The SPF number tells you how long the sun's UV radiation would take to redden your skin when using the product exactly as directed versus the amount of time without any sunscreen. So ideally, with SPF 30 it would take you 30 times longer to burn than if you weren't wearing sunscreen.
According to the Skin Cancer Foundation, 3% of UVB rays can enter your skin with SPF 30, and 2% with SPF 50. This is also how you can still get tan while wearing sunscreen. For the best protection, it's recommended that you choose a water-resistant sunscreen that is at least SPF 30 or higher every day.
The SPF rating only refers to UVB rays. An SPF 15 sunscreen blocks 93% of UVB radiation, and SPF 30 blocks 97%. After that, the difference in protection is small. SPF 50 blocks 98%, and SPF 100 stops 99% of UVB rays from reaching your skin.
A sunscreen with SPF 30 will protect you from around 96.7% of UVB rays, whereas an SPF of 50 means protection from about 98% of UVB rays.
The National Center for Biotechnology Information (NCBI) states that when a product with SPF 50 is applied, it will protect the skin until it is exposed to 50 times more UVB radiation than that is required to burn the unprotected skin.
Another mistake: using spray sunscreens incorrectly. “You can't just kind of spray it into the air and have your kid walk through it. It really needs to be sprayed directly on the skin,” said Wise. “And then the biggest mistake I see people make is not rubbing it in.
The SPF number estimates how long it will take your skin to burn when using the product as directed. If you normally burn in thirty minutes, wearing an SPF of 30 will instead take 900 minutes (when reapplied as directed) in the sun to cause a sunburn. If you use an SPF 50, it will take 1500 minutes.
Remember, the SPF of your sunscreen is not linked to how long you can stay in the sun, just to the amount of sun exposure you're protected from. Regardless of SPF, the protection will begin to wear off after a few hours. The advice from experts, therefore, is to reapply sunscreen every two hours.
“The UVL rays cause damage to our skin cells increasing the risk of skin aging and skin cancer. Using sunscreen on a daily basis is critical to protect the skin cells from this damage. This includes cloudy days when up to 80% of the UVL rays will penetrate through the clouds.”
How do you know if sunscreen is working?
If you don't get burned, it's working. Or, if you're a person who only tans and never burns, you don't get tanned. If you want to test it, wear an SPF 35 or higher broad-spectrum sunscreen for a couple of weeks when you're going to be outside in the summer sun, but leave a patch on your arm uncovered.
Unfortunately, many people only think to use sunscreen on scorching hot days, or if they're going to be outside all day. In reality, sunscreen should be applied every day, even if it is overcast outside or you're spending much of the day inside.
Sunscreen does not prevent you from tanning, because it does not protect your skin from 100% of UVA radiation. Applying SPF 30+ protects you from 97% of UV rays, while SPF 50+ from 98%. This means that some rays will still reach your skin despite wearing sunscreen, so it will not prevent tanning completely.
Additionally, natural processes such as perspiration and sebum production may disrupt the even distribution of sunscreen on your skin over time. Consequently, reapplication every two hours becomes essential for ensuring continued UV protection throughout prolonged periods of sun exposure.
Ask the Expert: How Often Do I Need to Reapply Sunscreen If I'm Indoors All Day? Sunscreen is an important part of a complete sun protection strategy, and it's essential to reapply throughout the day to ensure you're getting the most out of the product you choose. Generally, I recommend reapplying every two hours.
