SPF (sun protection factor) is a relative measure of how long a sunscreen will protect you from ultraviolet (UV) B rays. The chief cause of reddening and sunburn, UVB rays tend to damage the epidermis, skin’s outer layers, where the most common (and least dangerous) forms of skin cancer occur. Those cancers are linked to sun-accumulation over the years. Another type of skin cancer, melanoma, is thought to be caused by brief, intense exposures, such as a blistering sunburn.

Assuming you use it correctly, if you’d burn after 20 minutes in the sun, an SPF 50 sunscreen may protects for up to 16 hours, yet intensity and wavelength distribution of UVB rays vary throughout the day and by location thus it is recommended to apply every 2 hours.

UVA rays are long enough to reach skin’s dermal layer, damaging collagen and elastic tissue. That layer is also where the cells that stimulate skin darkening are found; that’s why UVA rays are considered the dominant tanning rays. (UVA rays are also used in tanning beds.) Though many people still think a tan looks healthy, it’s actually a sign of DNA damage—the skin darkens in an imperfect attempt to prevent the further injury, which can lead to the cell mutations that trigger skin cancer.

Time takes to burn your skin x SPF number = Sun protection time

7 Things Your Dermatologist Wishes You Wouldn’t Do


Flake out about sun protection

Say you’ve trained for a marathon covered in layers. Come race weekend, you might forget to put sunscreen on your packing list, even if it’s hot outside.

Big mistake. Sweating in the sun for three or more hours not only burns you to a crisp, it also increases your risk of melanoma and other skin cancers.

Planning is also required for training runs. Even if you start in the dark early-morning hours, you’ll probably be going for a while after the sun rises. And if it’s cloudy when you start, the sun may poke through later. Plus, you can still burn on an overcast day. So slather on the sunscreen and take your hat and sunglasses with you regardless of the conditions when you begin.


Be a miser with the sunscreen

Remembering sunscreen is only half the battle. You have to use it properly to reap the full SPF listed on the package.

If you choose a cream or lotion formula, that means spreading on at least a shot glass-sized amount. That’s about 40ml, so if you do the math, a 200ml bottle of sunscreen should disappear within about a weekend. If you are using the same bottle for the entire summer, you’re not protected. Aerosol Sprays are a convenient alternative, make sure not to miss any spots!



If there’s one myth that needs to be banished, it’s the idea that a little darkening now will protect you from sunburn or sun damage later on in the season.

Think of it this way: Tans and burns serve as your body’s built-in alarm system for when it’s time to get out of the sun.  Tanned skin is damaged skin. It doesn’t at all look healthy. And it looks even worse as the years pass.

Sun exposure accelerates the development of lines, wrinkles, and other signs of ageing.


run shirtless

We get it, it’s hot – and so are the other runners you pass on the path. But whether your motivation is to cool down or show off, think twice before you disrobe.

Many manufacturers now make clothes with sun protection built in – look for the term “UPF” on the label. And even regular shorts or tanks provide some protection, equivalent to a sunscreen with an SPF of about 8.

Stripping down robs you of that safeguard. And in most cases, you probably didn’t apply sunscreen to your stomach or back before you headed out, leaving you even more vulnerable to the sun’s damaging rays.


Forget about your head and lips.

In men with thinning hair, many skin cancers and pre-cancerous growths appear first on the scalp. It’s a spot that’s particularly dangerous, because any remaining hairs can conceal them and you probably don’t spend much time staring at the top of your head in the mirror.

Applying sunscreen to your dome – or if your hair’s thick, to your part – can help. Even better, wear a hat. Your scalp will stay safe and the brim can provide shade to your forehead. That means you can lighten up on sunscreen there to prevent it from running into your eyes.

Another frequently overlooked spot: your lips, which can burn just like the skin anywhere else. Smear your sunscreen over them or use a lip balm with SPF, and wear sunglasses – they protect your eyes and the skin around them from cancer and cataracts.


Suffer through a severe sunburn

That red, painful tissue serves as a sign your skin’s natural cling-wrap-like barrier is damaged. That makes it easier for illness-causing bugs to get through and harder for your body to regulate fluids and temperature If you feel feverish or have chills, nausea, headache, or other flu-like symptoms after getting a bad burn, seek medical treatment.

Same goes for burns that blister and cover large areas of your body, or that don’t get better after a few days of in-home treatment with strategies like cool rinses and pain-relieving medications.

Dermatologists or other doctors can prescribe steroid creams that speed healing. And in truly severe cases, you might even require hospitalization to receive intravenous fluids or other burn treatments.


Pop your blisters the wrong way

You don’t have to let that fluid-filled bulge go unattended, Keith says. Here’s how to relieve the pressure safely: Use a needle dipped in alcohol – not singed in a match, which doesn’t really work to sanitise it. Poke a hole and drain the fluid out, but don’t disturb the dead skin on the top of the blister any further. As tempting as it is to pull that off, it’s a biological dressing covering the healing skin underneath. Once you’re done, wash the affected area and cover it with petroleum jelly and a bandage. Skip the antibacterial cream – it’s far more likely to cause a rash or other irritation than it is to reduce a blister’s low risk of infection.



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