How much sunscreen is enough, sun protection, UVB radiation, and more myths

Skin cancer and melanoma (its most serious type) are linked with exposure to the sun’s rays. What should your sunscreen’s Sun Protection Factor (SPF) be? If you are already tanned, are you protected? What kind of radiation is harmful?
Read on and always stay safe under the sun’s rays.


“I can be protected if I only apply sunscreen once a day”

Where does the myth come from?

Sunscreen products work by absorbing or reflecting some of the sun's ultraviolet (UV) radiation and thus they help us protect against sunburn. Sunscreens can be used to prevent some forms of cancers. However, we must know how to apply them in order to be fully protected.

The reality behind the myth

Sunscreen works for a limited time. You should reapply sunscreen every two hours or according to the directions on the product label. Sunscreen should always be reapplied after swimming or participating in any activity that causes perspiration. Water-resistant sunscreens need to be reapplied every 40 or 80 minutes, according to the product label.


“I can be fully protected from the sun using sunscreens and tanning oils”

Where does the myth come from?

It is true that the most important way to prevent skin cancer is to protect the skin from the harmful effects of the sun's rays. Today, the majority of sunscreens and tanning oils claim to be able to protect the skin.

The reality behind the myth

Experts recommend the use of a broad-spectrum water-resistant sunscreen (which protects against both UVA and UVB rays), with a sun protection factor (SPF) of at least 30. SPF indicates the extent of protection from each sunscreen: the higher the SPF, the greater the protection. The SPF label shows the protection against UVB, which leads to sunburn and the damage that can cause skin cancer. It is also important that your high SPF sunscreen should also have a high level of UVA protection. UVA can cause ageing of the skin as well as damage it in a way that can cause skin cancer. However, no sunscreen is 100% effective and so it provides less protection than clothes or shade.



“My sunscreen’s SPF label is 30. I am fully protected from the sun.”

Where does the myth come from?

SPF or Sun Protection Factor is a measure of a sunscreen's ability to prevent UVB from damaging the skin. If it takes 20 minutes for your unprotected skin to start turning red, using an SPF 15 sunscreen theoretically prevents reddening 15 times longer, meaning about five hours. As a result, people believe that using a sunscreen of SPF 30 is more than enough for their protection from the sun.

The reality behind the myth

No sunscreen, regardless of strength, should be expected to stay effective longer than 2 hours without reapplication. Also, "reddening" of the skin is a reaction to UVB rays alone and tells you little about how much UVA radiation you may be getting. Plenty of damage can be done without the red flag of sunburn being raised.

There are three key points that debunk this common myth:

1. If you do not apply enough sunscreen (1 ounce for your body –the size of a ping-ping ball- and 1 tablespoon for your face) or you apply your sunscreen incorrectly, it may result in a lower SPF than the labeled protection level. For instance, if you under-apply your SPF 30 sunscreen by half, you may only get the protection level of an SPF 15 or lower. In this case, higher SPF sunscreens can help compensate for the fact that people usually do not apply enough.

2. Higher SPF sunscreens provide additional sunburn protection under extreme UV conditions. When you participate in moderate outdoor activities such as jogging or are outside on a very hot day, the heat from your activity and surroundings can increase the sensitivity of your skin and higher SPF protection is needed in order to prevent severe sunburn.

3. UV damage accumulates over your lifetime. Using a high SPF sunscreen can reduce the accumulation of chronic UV damage that is linked to non-melanoma skin cancer and aging.

High SPF sunscreens used to be known as thick and greasy, but today’s sunscreens have greatly improved and are even offered in spray forms so there is really no excuse to provide yourself the added protection.


“Tanning can actually protect from skin cancer”

Where does the myth come from?

A frequent message from the tanning industry is that a tan offers protection against sunburns.
It is true that as the skin tans, it produces a dark-colored pigment, melanin; this acts as a small shield against further damage from UV radiation. However, this offers very limited protection against sunburns: a dark tan on a white skin offers a sun protection factor of between 2 and 4. Clearly, this is not adequate defense against long-term UltraViolet (UV) damage, like skin cancer.

The reality behind the myth

A so-called “base tan” may delay sunburn, but it will not prevent damage from ultraviolet radiation. In fact, as the body attempts to defend itself against previous exposure to ultraviolet radiation, this radiation has already damaged the DNA in suntanned skin. This DNA damage can lead to mutations that cause cancer. Also, a substantial amount of ultraviolet radiation will still penetrate any tan.
Whether caused by sunlight, a tanning bed, or a sun lamp, no tan leaves your skin healthier than it was before.


“Only UVB radiation can cause skin damage”

Where does the myth come from?

Exposure to ultraviolet (UV) radiation is a major risk factor for most skin cancers. Sunlight is the main source of UV rays. People who get a lot of UV exposure are at greater risk of skin cancer.

Even though UV rays make up only a very small portion of the sun’s rays, they are the main cause of the sun’s damaging effects on the skin. UV rays damage the DNA of skin cells. Skin cancers start when this damage affects the DNA of genes that control skin cell growth.

There are 3 main types of UV rays: UVA, UVB and UVC rays. UVB rays have slightly more energy than UVA rays. They can damage skin cells’ DNA directly, and are the main rays that cause sunburns. They are also thought to cause most skin cancers.

The reality behind the myth

Both UVA and UVB cause sunburns and damage skin, possibly leading to skin cancer. UVB rays are a more potent cause of at least some skin cancers, but based on what’s known today, there are no safe UV rays. In all cases physicians recommend the use of a broad-spectrum sunscreen offering protection against both UVA and UVB rays. 


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Other sources include, American Society for Dermatologic Surgery and MD Anderson Cancer Center


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