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Dr. Marina Udowenko Discusses Sunscreen and Staying Sun-Safe


We sat down with Dr. Marina Udowenko (a.k.a. Dr. Marina) to talk about sunscreen and staying sun-safe.

NHN: Dr. Marina thanks so much for speaking with us today! When I was growing up I don’t remember my parents being particularly zealous about sunscreen, have attitudes about sunscreen usage changed since the 1980s, when we were all kids?

Dr. Marina: Yes, in part because we have learned more about the harmful effects of the sun’s rays.

NHN: Why is it important to use sunscreen?

Dr. Marina: Sunscreen is recommended to prevent sunburn. Sunburn is an acute inflammatory response of the skin from exposure to ultraviolet (“UV”) radiation from natural light sources, like the sun, or artificial light sources, like a tanning bed. Because sunscreen helps to prevent sunburn, it helps to prevent skin damage from exposures to the sun’s UV rays and can help to prevent early sings of aging. Too much UV radiation damages the cellular DNA of the skin which can lead to genetic mutations that can result in skin cancer. The US Department of Health and Human Services, along with the World Health Organization, have identified UV rays as a proven human carcinogen. UV radiation is considered the main cause of non-melanoma skin cancer and it also plays a role in melanoma. Melanoma kills more than 8,000 people a year.

NHN: What are UV rays?

Dr. Marina: UV radiation is part of the electromagnetic, also known as the light, spectrum that reaches the earth from the sun. The wavelengths are shorter than visible light and therefore cannot be seen by the naked eye. There are three types of UV rays: UVA, UVB, and UVC.

UVA rays are the longest with a wavelength of 320-400 nm. UVA accounts for up to 95% of the UV radiation reaching the Earth’s surface. UVA rays are present year round and can penetrate glass and clouds. UVB rays have a wavelength of 290-320 nm. UVB rays make up about 5% of the UV radiation reaching the Earth’s surface. UVB waves are responsible for sunburn. UVB intensity is greater around the equator, so latitude plays a role in an individual’s exposure. UVB exposure also varies by month – October to April is when we see the most significant amount of UVB radiation hitting the Earth. However, UVB rays can cause skin damage and sunburn year round, especially at higher altitudes and on reflective surfaces like snow and ice. In fact, snow and ice bounce back 80% of the rays so it is almost like they hit the skin twice. It is really important to use sunscreen year round – it is not just a summer necessity. Finally, UVC rays have the shortest wavelength. You don’t really hear much about these because they are mostly absorbed by the ozone layer and don’t reach the Earth.

NHN: What are the effects of UVA/UVB rays on the skin?

Dr. Marina: UVB tends to damage the outer layer of the skin and plays a key role in the development skin cancer and contributory role in tanning and premature aging. UVA penetrates the skin more deeply than UVB rays and reaches the dermal layer. It is a culprit of skin aging and wrinkles and can cause damage to the cells in the top layer of your skin where most skin cancers occur. Tanning salons utilize UVA rays. A tan actually results from damage to the skin’s DNA. Using a tanning salon is a really bad idea – patients who use tanning salons are 2.5 times more likely to develop squamous cell carcinoma and 1.5 times more likely to develop basal cell carcinoma. It can also increase the risk for melanoma by 75%.

NHN: Why are we always told to stay out of the sun between 10am to 2pm? What is so magical about that time?

Dr. Marina: The risk for sunburn is the highest during that time because it is when the UVB to UVA ratio is the highest. I tell my patients to avoid the sun from 10 am to 4 pm.

NHN: Now that you have firmly convinced me that I need to wear sunscreen all the time, what should I be looking for?

Dr. Marina: You want to look for a sunscreen that protects against both UVA and UBV rays with an SPF of at least 15.

NHN: What does “SPF” mean?

Dr. Marina: SPF means sun protection factor. It measures the amount of protection against UVB rays. The number indicates how long UVB rays will take to redden the skin when using a sunscreen versus using nothing at all. SPF 15 protects against 93% of all rays. SPF 30 protects against 97% of rays. SPF 50 protects against 98% of rays. Nothing provides 100% protection.

NHN: What are the different types of sunscreen?

Dr. Marina: There are really two types: chemical sunscreens and physical sunscreens. The majority of sunscreens on the market are chemical which work by creating a thin, protective layer on the surface of the skin and absorb UV radiation before it penetrates the skin. Physical sunscreens, also called mineral sunscreens, are insoluble particles that actually reflect the UV away from the skin. There are two types of mineral sunscreens: titanium dioxide, which has been shown to protect against UVB and UVA rays; and zinc oxide, which has been shown to protect against UVB and UVA as well. Technically zinc oxide protects against more versions of UVA rays, but that gets really technical.

NHN: Other than how the sunscreens work, is there a difference between a chemical sunscreen and a mineral sunscreen?

Dr. Marina: Yes. There is a 2009 study from UC Davis and the Environmental Working Group that purported to show that some chemical sunscreen ingredients are absorbed into the blood and are linked to toxic effects. The ingredients also could release skin-damaging free radicals in sunlight or disrupt hormone systems. Several of the sunscreens that the study looked at were linked to allergic reactions. The data from a 2003 study from UC Riverside also suggested that certain chemical sunscreen ingredients – this study looked at three chemical sunscreens – may cause free radicals to form. Free radicals disrupt cell functioning and are believed to lead to many cancers. Free radicals are reactive molecules that cause oxidative damage to cell walls, lipid membranes, and genetic material inside skin cells. This can lead to skin damage and increased visible signs of aging. But, it’s not just chemical sunscreens that have negative study data. Some studies have shown that titanium dioxide nanoparticles may not be safe. Nano-particles are ultra-microscopic in size which means they can easily penetrate your skin and travel to underlying blood vessels and your bloodstream. Some newer studies are suggesting that nanoparticles of titanium dioxide may induce toxic effects in your brain and cause nerve damage. Some data suggests they may also be carcinogenic. I need to add a qualifier about data and studies – studies can be done and published and that doesn’t mean that the study is of good quality. When you are looking at a study, or if you go back and look for the studies that I referenced, you want to see how it is set up (e.g., double-blind), how many subjects, and the components of the study (e.g. human skin or bioengineered skin). Don’t believe anything until you break down the study.

NHN: That is really helpful advice about studies. So, what type of sunscreen do you recommend in your practice?

Dr. Marina: I recommend physical, mineral sunscreens made with non-nano particles. I prefer zinc oxide because of its safety profile – it is FDA approved for infants in diaper rash cream.

NHN: When should sunscreen be applied/worn?

Dr. Marina: Sunscreen should be applied about a half-hour before going outside. This gives your skin enough time to absorb it. You should wear it every day.

NHN: How often should it be applied?

Dr. Marina: Sunscreen tends to be broken down by the skin so reapplication is paramount. The recommendation is to reapply sunscreen every 2 hours outdoors and right after swimming or sweating. I typically recommend reapplication at least every hour.

NHN: How much sunscreen do you need to use?

Dr. Marina: You need about an ounce, or two tablespoons.

NHN: What other measures should be taken to stay “sun safe”?

Dr. Marina: Wear sunglasses! Sunscreen does not protect your eyes and UV rays can damage your eyes leading to varying types of cancer and macular degeneration. I also recommend a wide-brimmed hat (at least 3 inches) and trying to stay in the shade as much as possible. Protective clothing is also a good idea. Infants under six months should be in the shade at all times. If that isn’t possible, you could apply a very small amount of sunscreen to the face or backs of the hands if other protective measures aren’t available.

NHN: Dr. Marina, thanks so much for your time!

Dr. Marina: No problem, thanks so much for chatting!

Dr. Marina is a Pennsylvania native and a graduate of the University of Pittsburgh. She attended medical school at Nova Southeastern University in Ft. Lauderdale, FL and completed her residency at the Baylor College of Medicine in Houston, Texas, and the University of Connecticut. Her active lifestyle which included running and swimming inherently sparked her interest in sports medicine. It was during her medical mission trips to Haiti, Nicaragua, and the Dominican Republic where her interest in dermatology was ignited. She sought to complete training in dermatology to understand skin disease and preventative measures to maintain healthy skin through time. Upon completion of her sports medicine fellowship at Wake Forest University, she continued to pursue rotations in dermatology. Dr. Marina went on to complete additional training with the American Academy of Aesthetic Medicine, National Laser Institute, National Institute for Medical Aesthetics, as well as an internship in aesthetic medicine. Her passion and joy lie in blending artistry and exciting, new emerging technologies to achieve healthy, well-nourished beautiful skin from the inside out. Dr. Marina maintains a practice in San Diego, California. You can learn more about her practice here.


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