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Sunscreen

Please Shine Down on Me: The Skinny on Sun Exposure

July 2, 2020


We all know that sun exposure can cause skin cancer. We have heard the public service announcements and we have seen the advertisements for sunscreen that emphasize regular use to prevent cancer. We have had the inquiries when we see our primary care providers and have wondered about the size and shape of moles on our bodies. We are not confused about the potential deleterious effects of the sun on our skin. However, many of us are confused about the details that underlie these effects, our protection & the best mode of prevention. SPF numbers have increased to now represent seemingly impossible integers, UV light has been split into different nebulously risky categories, and we have been told that sunscreen is destroying oceanic habitats. It would be hard, with so many mixed messages and so much conflicting information coming at us, to not be confused about our best approach to staying safe while enjoying the PNW's limited summer sun. Here are the answers to six frequently asked questions/concerns about UV exposure that may help clarify the murkiness of managing the risks associated with sun exposure:


1. What harm can come of UV exposure? It's just the sun.

The sun itself is not a problem. It is beautiful, warming, glorious. Exposure to the sun improves our moods & can actually improve our overall health. The rays of UV radiation emitted by the sun are the cause for concern & the concerning thing about the UV radiation is the kind of energy it produces. These rays have more energy contained in them than visible light but less energy than X-ray radiation, which is known to cause various kinds of cancer with repeated exposure. UV radiation itself does not itself produce a specific amount of radiation. There are variations in the radiation exposure based on the different wavelengths of UV rays. Higher-energy UV rays are a form of ionizing radiation. This means they have enough energy to remove an electron from (ionize) an atom or molecule. Ionizing radiation can damage the DNA (genes) in cells, which in turn may lead to cancer. But even the highest-energy UV rays don’t have enough energy to penetrate deeply into the body, so their main effect is on the skin that they do penetrate. This is why we worry about skin cancer developing in response to sun exposure. Most skin cancers are a result of exposure to the UV rays in sunlight. Both basal cell and squamous cell cancers (the most common types of skin cancer) tend to be found on sun-exposed parts of the body, and their occurrence is typically related to lifetime sun exposure. The risk of melanoma, a more serious but less common type of skin cancer, is also related to sun exposure, although perhaps not as strongly. Exposure to UV rays can also cause premature aging and sun damage to the skin, including wrinkles, texture changes, brown spots & raised lesions. UV rays can also cause eye problems, including inflammation or the cornea, formation of cataracts or growth of tissue on the surface of the eye that impairs vision. Excessive UV exposure can also weaken the immune system, making it harder for the body to fight off infections, which can cause such things as reactivation of dormant viruses.


2. Don't we need sun exposure to make Vitamin D?

Yes. Your skin makes vitamin D naturally when it is exposed to UV rays from the sun. How much vitamin D you make depends on many things, including how old you are, how dark your skin is, and how strong the sunlight is where you live. Vitamin D has many health benefits. It might even help lower the risk of some cancers. It is very difficult to get sufficient vitamin D from dietary sources or to absorb it well from oral supplements. It is important, therefore, to ensure that you do have some UV exposure during the day in order to successfully synthesize adequate amounts of Vitamin D. The amount of time required to synthesize sufficient vitamin D will depend on the amount of melanin in your skin; if your complexion is fair, you do not need more than 25 minutes of direct exposure to the sun, but if your complexion is darker, you may require 40-60 minutes of exposure. This amount of exposure to the sun should not significantly increase your risk of cancer. Beyond those recommended times of exposure, you continue to synthesize more vitamin D, but your risk of harmful UV radiation effects increases.


3. Is higher SPF better?

Not necessarily. SPF stands for sun protection factor. The SPF number represents the level of protection the sunscreen provides against UVB rays, which are the main cause of sunburn and are the primary source of damaging UV radiation. A higher SPF number means more UVB protection (although it says nothing about UVA protection). What the SPF number means is that you get 1 minute of UVB protection for that number of minutes spent in the sun (it decreases the amount of overall exposure by that number of minutes). For instance, when applying an SPF 30 sunscreen correctly, you get the equivalent of 1 minute of UVB ray protection for each 30 minutes you spend in the sun. So, 1 hour in the sun wearing SPF 30 sunscreen is the same as spending 2 minutes totally unprotected. People often do not apply enough sunscreen, so they get less actual protection. Sunscreens labeled with SPFs as high as 100+ are available. Higher numbers do mean more protection, but many people don’t understand the SPF scale. SPF 15 sunscreens filter out about 93% of UVB rays, while SPF 30 sunscreens filter out about 97%, SPF 50 sunscreens about 98%, and SPF 100 about 99%. The higher you go, the smaller the difference. There is no sunscreen available, despite the high SPF number, that confers complete protection from the possible harmful effects of the radiation emitted by the sun.


4. Is sunscreen more damaging than the sun?

There are two basic kinds of sunscreen: mineral & chemical. Mineral sunscreens are largely composed of one of two compounds: zinc oxide (think diaper rash cream) & titanium oxide. These minerals create a physical barrier or shield that sits on top of the skin & prevents deep penetration of UVA & UVB rays into the skin. Chemical sunscreens use a variety of different chemicals, which may include oxybenzone, avobenzone, octisalate, octocrylene, homosalate, octinoxate, or any combination of these compounds. The most common chemical sunscreen ingredient, oxybenzone, is an endocrine (hormonal) disruptor & its use is legally limited in many countries (not the US). Oxybenzone is also directly linked to damage, destruction & death to many oceanic creatures, including coral reefs & has been banned in such places as Hawaii to prevent further harm to underwater habitats. Many sunscreens also contain a compound called methylisothaizolinone, which is both an endrocrine disruptor & a potent skin allergen for many. The mineral sunscreens do not penetrate the skin itself & are minimally absorbed, as their purpose & function is to create a physical barrier between the sun & your skin. The chemical sunscreens, on the other hand, do deeply penetrate the skin in order to alter the skin's response to the sun & convert & denature UV radiation as it is penetrating the skin. It is well-established that chemical sunscreens have systemic absorption & effect, & many of these chemicals have been found in studies to be circulating in users' bloodstreams at more than 400% the recommended level. Things get even dicier when sunscreen becomes aerosolized & the compounds are now inhaled in small particles into a user's lungs & coat the membranes lining the lungs. We recommend being highly aware of what you are putting on your skin & how you are putting it there. We recommend using a mineral barrier sunscreen & applying it as a lotion or cream that allows you to control the site of application. We also recommend that you take the time to fully understand the chemical composition of anything you are putting onto or into your body & to grasp the risks of use. The environmental working group is a non-profit organization dedicated to evaluating potential environmental exposures that may have toxic potential for humans & is a great source of information regarding ingredients in many over-the-counter, off-the-shelf products available in the US.


5. What's the difference between various types of UV radiation?

There are three fundamental groups of UV radiation: UVA, UVB & UVC. Of these, UVA has the least amount of energy & therefore poses the lowest threat in terms of cellular damage. UVA radiation can cause skin cells to age & can cause some indirect damage to cells’ DNA. UVA rays are mainly linked to long-term skin damage such as wrinkles, but they are also thought to play a role in the development of some skin cancers. From an aesthetic perspective & in terms of preventing premature aging of the skin, these rays are the most important to avoid. UVB radiation is the middle-of-the-road in terms of energetic potential for UV radiation. These rays can damage the DNA in skin cells directly, & they are the main cause of sunburn. They are also thought to cause most skin cancers. Unfortunately, it is these same radiation that is responsible for provoking our skin's synthesis of Vitamin D. Therefore, it requires a very delicate balance of limited unprotected exposure to optimize our health benefits & risks. Broad-spectrum sunscreens protect against both UVB & UVA radiation. UVC radiation has the highest amount of energy of any UV radiation. These rays are so energetic that they react with ozone high in our atmosphere & generally don’t even reach the ground, so they are not normally a risk factor for skin cancer. However, UVC rays can also come from some man-made sources, such as arc welding torches, mercury lamps, & the UV sanitizing bulbs that are used to kill bacteria & other germs (such as in water, air, food, or on surfaces). There is no sunscreen in existence that protects skin or any other body part from exposure to UVC rays, which are invariably more damaging than UVB radiation.


6. If I tan easily or have darker skin at baseline, does sun protection still matter for me?

The short answer is yes. Regardless of the amount of melanin in your skin, it is still important for you to protect yourself against excessive exposure to UV radiation because of the invisible damage that can be done to the cells within your skin. Such damage is not rooted in the amount of available melanin. It is easier for individuals with fairer skin to experience burning more readily from sun exposure, & their sun-related risks are therefore greater. Women whose skin naturally has more melanin do have more innate cellular protection against UV radiation. However, having darker skin does not confer instant protection & is not a form of prevention for UV-associated harm. Women with large amounts of melanin can still burn their skin & there is some risk that they may not realize it when they have, as their skin is less likely to appear reddened & more likely to feel hot, sensitive & itchy. And, skin cancer, while less likely to occur in women with darker skin, is deadlier for browner ladies--they are more likely to have their skin cancers overlooked, diagnosed at later stages, & result in their death. Therefore, it may actually be MORE important for the darker skinned women among us to ensure that they are protecting themselves from UV damage. We recommend that women with all colors of skin have exposure to the sun each day. For fair individuals, we recommend limiting unprotected exposure or calculating exposure based on protection to an equivalent of less than 1 hour each day. As melanin production in the skin increases, based on genetics or reactivity to the sun (e.g., the tanning effect), that duration can gradually lengthen without increasing health risks related to exposure. However, even for the woman with the darkest skin on the planet, we do not recommend direct exposure to the sun for more than 2 hours.


There are many things other than sunscreen that matter for UV protection, including sun-protective clothing ( wide-brimmed hats, UPF-designed tops/leggings, umbrellas, other sources of shade), sunglasses & consideration of the UV index, which is a metric designed to convey the amount of risk associated with sun exposure at any given time of day in any given location of the world (check your weather statistics for your location's UV index). Skin isn't the only thing that can be harmed by UV exposure, so it is equally important to ensure that you are protecting your eyes with proper sunglasses that are specifically designed to block harmful rays. We want you to have fun in the sun, & we want you to enjoy the briefly glorious summer of the Pacific Northwest, but we also want to ensure you have proper protection & are not increasing your risk with your use of products intended to protect you. As always, we are available to answer any questions you might have, look at any moles that concern you, or treat any skin condition that has arisen.