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Protecting our skin from harmful ultraviolet (UV) light is a year-round job. It requires wearing the proper clothing, using sunscreen on exposed skin, and seeking shade when the sun¡¯s rays are at their strongest.?

But have you ever wondered what distinguishes regular, everyday clothing from the kind you see advertised as having a UPF, or Ultraviolet Protection Factor? Or, the difference between UPF and SPF, which is listed on bottles of sunscreen and other skin care products?

For answers to these and five other questions, we went to dermatologist , who serves as director of MD Anderson¡¯s Mohs Center. Here¡¯s what she shared with us.

What¡¯s the difference between SPF and UPF?

• SPF, or Sun Protection Factor, is based on the amount of time it takes for skin to start turning red after being exposed to UV light. The number indicates how many times longer than that a product applied to the skin might protect you, if used properly. So, if you¡¯d normally start to burn after about 10 minutes out in the sun, sunscreen with SPF 30 could theoretically extend that period by 30 times ¡ª or for up to five hours (300 minutes).
• UPF, or Ultraviolet Protection Factor, meanwhile, is a measurement of the amount of UV light that can reach your skin through a particular fabric. The number here represents the bottom part (denominator) of a fraction. So, if a bucket hat is advertised as having UPF 50+ protection, that means only about 1/50^th of the sun¡¯s UV rays ¡ª or 2% ¡ª can pass through it.

Another difference is that UPF blocks both UVA and UVB light. Unless a product is labeled ¡°broad spectrum¡± though, SPF technology only blocks UVB light. UVB light is the type that causes most sunburns and skin cancers. UVA light causes wrinkles and other visible signs of aging.

Why did you use the word ¡°theoretically¡± when talking about SPF?

I don¡¯t want to give anyone a false sense of security. And, I also don¡¯t want anyone who burns really easily doing the math and thinking they can stay on the beach for hours without any problem, just because they put on SPF 30 sunscreen once and never reapplied it.

The key phrase above was ¡°if used properly.¡± Most people only apply about one-third of the sunscreen they actually need. They use one tablespoon per application, when you really need three. That¡¯s the equivalent of a quarter cup!

Also, both swimming and sweating can make sunscreen wear off much faster, so it needs to be reapplied frequently. We recommend reapplying sunscreen at least once every two hours, but more often if you¡¯re playing in the water or perspiring profusely.

How does clothing made specifically to protect skin from UV light differ from regular clothing??

What makes these fabrics special is the material they¡¯re made out of, how tightly they¡¯re woven and, sometimes, how they¡¯re processed. Many of these garments are woven very tightly to block the sun¡¯s rays. Others are dyed with or soaked in special chemical solutions that basically give the fabric a natural sunscreen, such as zinc oxide.?

Applied coatings can fade over time, though. So, you may notice the colors changing or the fabrics getting stretchier as you wash these garments. Those could be signs that they¡¯re losing their UPF protection and need to be replaced.?

Check the label of each item or visit the manufacturer¡¯s website for details. Some garments are designed to retain their UPF for up to 100 or even 500 washes. Other manufacturers claim their garments¡¯ UV protection never wears out.?

Doesn¡¯t regular clothing protect us against UV light?

Your clothing¡¯s UPF value depends on the type of fabric it¡¯s made out of, the color of the fabric and whether or not the fabric is wet. Dry, tightly woven, dark-colored fabrics offer the most protection.?

But the stretchier a fabric is, the less protection it offers, especially when fully extended. Something like dry, dark biking shorts start out at about UPF 85 before the material is stretched, and UPF 8 when worn. And, if they get wet, too, they drop even more, to UPF 4.?

A conventional bathing suit made out of dark, stretchy material has a UPF 8.6 when dry, while a white or light-colored bathing suit only offers about UPF 4 when wet. Most swimsuits provide about a UPF 5, so roughly 20% of the sun¡¯s rays will still reach your skin.

Does that mean we should all be putting on sunscreen before we put on our swimsuits?

No. The current recommendation is to apply sunscreen only to exposed skin. Just keep in mind that traditional bathing suits might not offer as much protection to covered areas as you think.?

Most of the Mohs surgeries I perform in the buttock fold area have one thing in common: they¡¯re all on people who are shocked. Many, however, have a history of sunning themselves face-down in a bathing suit. I also do a lot of Mohs surgeries on UV-associated cancers around sensitive genital skin, due to tanning bed use.

Is there any way to gauge how protective my regular clothing is?

Yes. One way is to hold it up to the sun. If you can see the sun¡¯s light through the fabric, then its UV rays are getting through. But the weave of a fabric matters. So, if you have something with a very tight weave and hold it up to a window, then you might not see the sun.?

If you¡¯re really concerned, you can always look for UPF 50+ swim garments that block 98% of the sun¡¯s rays. It¡¯s much easier to find swimsuits with sun-protective materials now than it used to be. It¡¯s also much easier to buy one of those than it is to try to put sunscreen everywhere.

According to the American Academy of Dermatology, any garment with a UPF between 30 and 49 is considered good protection, while a garment with a UPF 50 or higher is considered excellent protection. Anything under UPF 30 is not considered highly sun protective.?

Is there any way to add UPF to my clothing myself?

Yes. There¡¯s a colorless fabric dye you can use as a laundry treatment. You add one package to a load of laundry and let it soak. The effect is said to last for up to 20 washes. It¡¯s available at most fabric and craft stores.

or call 1-877-632-6789.

Sunscreen is a hot topic ¨C and not just because it¡¯s a summertime staple!

There are also many myths and misconceptions surrounding sunscreen¡¯s safety, effectiveness and usefulness.?

So, if you¡¯ve ever been confused about when ¨C or if ¨C to use sunscreen, you¡¯re not alone.

We asked dermatologist?, about common sunscreen myths. Read on for her answers.

Myth 1: All sunscreens work the same way.

False. Sunscreens can prevent sunburn in different ways.

Chemical sunscreens:?The active ingredients in chemical sunscreens absorb UV rays as they hit the skin, Patel explains.

Physical blocker sunscreens:?Physical sunscreens, which are also called?mineral sunscreens?or sun blocks, use ingredients such as zinc oxide and titanium dioxide to form a barrier on the skin¡¯s surface that reflects UV rays.

Not sure whether to use a chemical or physical sunscreen? Hybrid sunscreens contain both chemical absorbers and physical blockers.?

When selecting a sunscreen,?MD Anderson?dermatologists recommend choosing a?broad-spectrum?product with at least?sun protection factor?(SPF) 30. 'Broad spectrum' means the product protects from both UVA and UVB rays which can lead to sun damage and?skin cancer. SPF refers to the amount of UVB rays it blocks.

Myth 2: It doesn¡¯t matter what kind of sunscreen I choose.

False. While wearing sunscreen is always a good choice, each type of sunscreen has instructions that must be followed to ensure your skin is protected.?

Sunscreen comes in forms including cream, lotion, spray, powder and stick.

Each type of sunscreen has benefits and limitations. For example, many spray sunscreens are clear and absorb into the skin quickly, but this can make it challenging to see if you¡¯ve missed a spot.

Overwhelmed by options??MD Anderson?dermatologists recommend physical blocker sunscreens. Patel says this is because they have the broadest range of UVA and UVB protection.

Whatever type of sunscreen you choose, always review its instructions for information on how ¨C and how frequently ¨C to apply and reapply.

Myth 3: Sunscreen causes cancer.

False. There is no medical evidence that sunscreen causes cancer. However, there is a lot of evidence that UV rays from the sun and tanning beds do.

In the past, some sunscreens were recalled for being contaminated with a chemical called?benzene.?Benzene is not normally found in sunscreen. This recall doesn¡¯t mean you should stop wearing sunscreen, dermatologists say.

Still, some may feel more comfortable using sunscreens that don't absorb into the skin ¨C that is, those physical blockers sunscreens described above.

Additionally, sunscreen isn¡¯t the only way you can practice sun safety.

¡°There are a lot of sun protective options outside of just the creams and sprays,¡± Patel says.

Other ways to protect yourself from sun damage include:

• Wearing protective clothing that is dark and tightly woven, with ultraviolet protection factor (UPF) 50+
• Wearing a wide-brimmed hat
• Wearing sunglasses with UVA and UVB protection
• Seeking shade between 10 a.m. and 4 p.m. when sun rays are strongest

Myth 4: I have dark skin. I don¡¯t need to wear sunscreen.

False.?Dark skin?is susceptible to sun damage.

It takes more sun exposure for darker skin types to get sun damage, Patel says. She explains this is because melanin, which gives skin its color, provides DNA with a small amount of sun protection. Still, this small amount of protection doesn¡¯t prevent sun damage altogether.

¡°Darker skinned people can still get a sunburn, still get skin cancers and definitely still get photoaging from UV exposure,¡± Patel says.

Regardless of your skin color, apply sunscreen liberally 30 minutes before going out in the sun, and don¡¯t forget to reapply every two hours or after swimming or sweating.

Myth 5: My sunscreen is waterproof, so I don¡¯t need to reapply it after swimming or sweating.

False. According to the , there is no such thing as waterproof sunscreen.?

There is, however, water-resistant sunscreen. Check the product label to see how long it works for. Water-resistant products must say whether they are ¡°effective for 40 minutes or 80 minutes when swimming or sweating,¡± writes the FDA.?

Heading for a beach day or outdoor workout? Choose a water-resistant sunscreen and follow the product instructions on how often to reapply.?

Myth 6: My sunscreen is SPF 50, so I don¡¯t need to apply it as often.

False. No matter the SPF number, chemical absorber sunscreens only work for about two hours and should be reapplied after swimming or sweating.

Regardless of the SPF level you choose, you need to reapply with the same frequency, Patel says.

If you have trouble remembering to reapply, Patel suggests using a physical blocker sunscreen. These products don¡¯t rub in or disappear into the skin, so it is easy to determine when to reapply.

¡°If you can see the white on your face, it's still working,¡± she says.

Myth 7: There is SPF in my makeup. I don¡¯t need to wear sunscreen.

False. While Patel says that sunscreen in makeup counts, it usually doesn¡¯t provide the recommended SPF levels.

¡°It's typically only 5 to 15 SPF, and we recommend 30,¡± she says.

Check that your makeup offers at least 30 SPF, and use additional sunscreen as needed. Finally, don¡¯t forget to apply sunscreen to other exposed areas of your body, and make sure you reapply sunscreen as directed throughout the day.

Myth 8: I only need sunscreen in the summer or if it's sunny.?

False. Sunburn and sun damage may be associated with hot, sunny weather, but they can also occur in cold, cloudy conditions.?

¡°Even when it's cold, sun is getting through the clouds,¡± Patel says.??

While clouds filter some UVB rays, they don¡¯t block UVA rays, which are a risk factor for melanoma, she adds.?

Likewise, UV rays don¡¯t disappear in the winter. In fact, snowy winter activities can even increase your risk of sunburn.??

¡°Snow sports can be sneaky because you get the reflection off the snow as well as overhead exposure,¡± Patel says.?

Be especially cautious of sunburn at high altitudes, such as when you are skiing. At high altitudes, UV rays are less filtered by the atmosphere, which leads to more intense UV exposure, she adds.?

So, sunny or cloudy, hot or cold, summer or winter, apply sunscreen to any exposed skin just like you would if it were a warm, sunny day.?

Myth 9: I don¡¯t need sunscreen inside.?

False. Spending time indoors shouldn't mean skipping SPF. That¡¯s because UV rays can come through windows.??

¡°Most windows, unless they are tempered glass or have a UV-filtering film, allow passage of UV rays,¡± Patel says.?

Likewise, she notes that wearing SPF ¨C even on days you¡¯re mostly inside ¨C protects your skin from UV exposure you might not even recognize you¡¯re getting, like while driving or walking through the parking lot to the grocery store.?

¡°Most people would say they were inside all day, but there is cumulative incidental exposure that occurs,¡± she says.?

Myth 10: Sunscreen doesn¡¯t expire.

False. ¡°You cannot rely on expired sunscreen,¡± Patel says. ¡°Nothing bad is going to happen if you use an expired one in terms of increased toxicity. It just won't work.¡±

It is also important to store sunscreen properly. Specific storage instructions can be found in the product¡¯s ¡®Drug Facts¡¯ section.

For example, if you store your sunscreen in a hot car or in direct sunlight, Patel says the product could degrade earlier than its expiration date.

¡°You have to look at the storage recommendations. Sunscreen will only last until the expiration date if you keep it within those temperature ranges,¡± she says. ¡°If you go outside of those temperature ranges, the molecules that are protecting your skin will degrade faster.¡±

?or call?1-877-632-6789.

Normally, you probably hear health care professionals talk about ultraviolet (UV) light regarding sun safety.??

That¡¯s because exposure to the sun¡¯s UV light is connected to so many different types of skin cancer, including:?

• basal cell carcinoma
• squamous cell carcinoma
• melanoma

But did you know that UV light can sometimes be used to treat cancer or its side effects, rather than cause it? We spoke with stem cell transplant specialist , and dermatologist , to learn more. Here¡¯s what they shared.?

UV light therapy can be an effective cancer treatment?

As it turns out, UV light¡¯s ability to damage cells is precisely what makes it useful in cancer treatment.??

Some forms of UV light can be used to treat a form of cutaneous T cell lymphoma called mycosis fungoides. It can also help manage skin rashes caused by cancer treatments, allowing patients to stay on them for longer.?

¡°It may sound counterintuitive,¡± Huen says, ¡°but UV light can actually be helpful. A lot of patients do very well on it. It¡¯s a very effective treatment.¡±??

So, how does it work??

Option 1: Using UV light ¡®indirectly¡¯

Let¡¯s take a look at extracorporeal photopheresis first. This process uses a special chemical to sensitize certain immune cells to the DNA-damaging effects of ultraviolet light. It¡¯s the same principle as chemoradiation, which uses chemotherapy to sensitize cancer cells to the effects of radiation therapy.?

The main difference is that while chemoradiation is applied directly to the body, extracorporeal photopheresis takes place entirely outside of it.??

¡°Extracorporeal photopheresis does not expose you directly to UV light,¡± explains Hosing.??

Instead, your blood is drawn into a special apheresis machine, injected with a photosensitive agent called 8-methoxypsoralen (8-MOP), and exposed to a concentrated dose of UV light before being returned to your circulatory system.?

¡°This modulates the function of immune cells so that they cannot keep causing inflammation,¡± adds Hosing.? ?

The uses of extracorporeal photopheresis

The Food and Drug Administration (FDA) approved both the extracorporeal photopheresis device and the sensitizing agent for treating various conditions and side effects in 1988. Currently, it is used to treat:?

• an aggressive subtype of cutaneous T cell lymphoma called S¨¦zary syndrome??
• graft vs. host disease (GVHD) in allogeneic stem cell transplant recipients??
• solid organ transplant rejections in patients who¡¯ve received donated hearts or lungs?

¡°There have been some clinical trials testing extracorporeal photopheresis for the treatment of other skin conditions, too, such as vitiligo (a condition that causes blotchy skin) and atopic dermatitis,¡± notes Hosing. ¡°But none of those have really panned out.¡±?

Option 2: Using direct UV light exposure

Surprisingly, patients with a form of cutaneous T cell lymphoma called mycosis fungoides are sometimes asked to expose the affected skin to direct sunlight or a UV lamp. The latter is a practice known as phototherapy or ¡°box therapy.¡±??

¡°Doctors sometimes tell their patients to sit outside for 20-30 minutes a day, with the affected skin exposed,¡± explains Hosing. ¡°That¡¯s considered helpful when the disease is minimal and limited to small areas. But if you have S¨¦zary syndrome and it involves the blood, then you¡¯ll need systemic treatment. Just exposing the surface of the skin to UV light won¡¯t be enough.¡±?

The uses of phototherapy

Phototherapy is sometimes administered in a doctor¡¯s office when patients are unable to reliably expose their skin to the sun. It is sometimes called ¡°box therapy¡± because patients must stand or lie naked inside a special windowless chamber to receive the UV light therapy. But don¡¯t be confused if you go in for treatment one day and think that the ¡°box¡± looks just like a tanning booth.?

¡°While the devices might look similar, they are not the same thing,¡± explains Huen. ¡°The machines at tanning salons are not well-supervised and not designed for medical use. In a doctor¡¯s office, patients receive a controlled dose of the safest wavelength of light, gradually adjusted to their specific needs.¡±?

In addition to mycosis fungoides, phototherapy is used to treat:?

• dermatitis?
• psoriasis?
• eczema?
• rashes caused by targeted therapy or immunotherapy??

¡°Obviously, it might not be the best choice if someone has had melanoma or skin cancer,¡± Huen explains. ¡°But if you¡¯re being treated for a totally different type of cancer and struggling with severe skin-based side effects, this might offer you just enough relief to continue with systemic therapy.¡±?

The best candidates for phototherapy

Not every person with a qualifying condition will be a good candidate for phototherapy.?

¡°This also wouldn¡¯t be the best choice if you¡¯ve only got one tiny little spot on your hand,¡± notes Huen. ¡°At least 10-20% of your skin must be affected. Rashes and other skin conditions have to be pretty extensive and not be getting any better with creams or lotions in order to justify full-body exposure.¡±?

Phototherapy can also be used to help patients avoid or delay systemic therapy for cutaneous T cell lymphoma ¡ª and the side effects that come with it.?

¡°Since phototherapy is applied directly to the skin, it has few side effects,¡± Huen explains. ¡°That allows some patients to delay systemic treatment indefinitely.¡±?

or call 1-877-632-6789.

Sunscreen helps protect your skin from ultraviolet (UV) radiation. But which SPF is best?

MD Anderson dermatologists recommend sunscreen that is at least SPF 30, broad-spectrum and water resistant. Even with those guidelines, there are plenty of options to choose from. They may even prompt questions like, ¡°If SPF 30 is good, does that mean SPF 50 or even SPF 100 is better?¡±

I always like to remind patients that sunscreen ¨C no matter what SPF you choose ¨C is only one part of sun protection. Ahead, we¡¯ll talk about SPF and how to use it as part of a larger sun safety routine.

How is SPF determined?

SPF levels are determined by laboratory testing. Sunscreen is applied to a designated patch of skin before it¡¯s exposed to an ultraviolet light source that simulates sun exposure. Then, the time it takes the sunscreen-protected skin to redden or burn is carefully measured and compared with the time it takes a similar area of unprotected skin to redden or burn. The testing protocol specifies everything from the amount of sunscreen applied per area of skin to the type of light source that is used. This is done to standardize measurements and make it easier for shoppers to compare sunscreens using their SPF levels.

In laboratory SPF testing, small areas of skin are covered in a uniform, thick layer of sunscreen. But real-life conditions ¡ª like a day at the beach or an afternoon spent by the pool ¡ª are not controlled like they are in the laboratory. People tend to underapply sunscreen, apply it unevenly and forget to reapply it before it wears off or gets rubbed off. Likewise, conditions like the intensity of UV exposure can change. This means most of us won¡¯t reach the sunscreen¡¯s level of SPF in everyday use.

How much protection does SPF provide?

Sunscreens help protect our skin by reflecting or absorbing the ultraviolet rays that cause sunburn and skin damage. SPF numbers give us an idea of how much protection a sunscreen provides and how it compares to other sunscreens. A higher SPF means a sunscreen can absorb or reflect more sunburn-causing UVB rays to prevent you from getting burned than a lower SPF sunscreen can.

Double the SPF number doesn¡¯t mean double the protection, however. This is because the amount of UVB blocked by sunscreen is not linear. In other words, after a certain point, a higher SPF number may only provide a little more UVB protection.

For example,

• SPF 15 blocks 93% of UVB rays
• SPF 30 blocks 97% of UVB rays
• SPF 50 blocks 98% of UVB rays

Likewise, after a certain point, less extra UV exposure is needed to cause more damage to your skin.

Think of it like layering clothes in a blizzard. The first few layers make a huge difference in blocking the cold. After that, the third and fourth layers provide additional protection, but proportionally less than the first layers did.

What do these sunscreen terms mean?

Sometimes it can seem like you need a dictionary to read sunscreen packaging. Here¡¯s what some common sunscreen terms mean.

Broad-spectrum

MD Anderson?dermatologists recommend choosing a broad-spectrum sunscreen. This means that the sunscreen protects from two different types of sun rays that can damage skin: UVA and UVB.

UVA exposure?leads to skin tanning, pigmentation and oxidative damage that can contribute to photoaging and add to the cancer-causing effects of UVB.

UVB exposure?is the main cause of sunburn and can lead to?skin cancers,?including?melanoma,?basal cell carcinoma?and?squamous cell carcinoma of the skin.

Water-resistant

If you are swimming, sweating or splashing,?MD Anderson?dermatologists recommend choosing a water-resistant sunscreen. The??(FDA) regulates sunscreen products and writes that water-resistant products are labeled as providing their SPF levels for either 40 or 80 minutes, even in wet conditions.

Don't forget: You still need to reapply water-resistant sunscreen just as frequently as sunscreen that isn¡¯t water-resistant.

PA++++

Sunscreens labeled as ¡®broad-spectrum¡¯ have been tested to protect against UVA and UVB rays. The PA++++ index is a newer, separate rating that means additional testing was done to quantify how much UVA protection a sunscreen provides. It is based on a number called the UVA-Protection Factor (UVA-PF), which is like SPF but for UVA rays. The ranking goes from less protective to more protective: PA+ to PA++++. So, choose PA++++ for the most UVA protection.