For many people, spending time outdoors is a lot of fun. For some, it’s a daily way of life. Whether you frequently venture outside for recreation or you work outside, some amount of sun exposure is simply unavoidable. Everyone reacts differently to sun exposure. Some people tan easily and rarely burn, no matter how long they stay outside. Others burn easily and must always wear sunblock.
Your risk of sunburn may be lower or higher, depending on your skin pigmentation and other factors. Generally, people with fair skin are at higher risk for sunburn. However, even darker complexions can experience sun damage, especially with frequent, long-term exposure. UV exposure varies from location to location. For example, there is a greater risk of sunburn at higher elevations and in areas that frequently experience a high UV index.
According to SkinCancer.org, about 90 percent of non-melanoma skin cancers and about 86 percent of melanomas are associated with exposure to the sun’s ultraviolet rays. Although cancer is the scariest potential outcome of sun exposure, there are other potential consequences. Over time, the long-term effects of sun damage can cause uneven skin pigmentation, dark spots, wrinkling and even loose skin.
The bottom line: Anyone can experience health problems associated with sun exposure, regardless of skin tone. Protecting yourself from the sun’s UV rays is the best way to minimize health risks.
One of the most common sun protection questions is about the difference between SPF and UPF. What exactly do these terms mean? Although similar, these acronyms refer to two different sun protection ratings.
What is SPF?
SPF stands for Sunburn Protection Factor. SPF is the standard used in the United States to rate how much UV radiation a sunscreen lotion or cream will block. The FDA has established standards for testing over-the-counter sunblock and suntan lotions, and the FDA requires companies to accurately label sunscreen SPF according to these test results. The two types of UV radiation that pass through the earth’s atmosphere are UVA and UVB. According to Dr. Steven Wang, director of dermatologic surgery and dermatology at Memorial Sloan-Kettering Cancer Center, UVB plays a predominant role in causing the skin damage that can lead to skin cancer. For this reason, the SPF rating of a sunscreen should refer to its ability to block UVB rays. For example, SPF 15 sunscreen should block about 93 percent of UVB radiation. SPF 30 sunscreen should block about 97 percent. Keep in mind that these ratings are based on suitable application: about two milligrams of sunscreen per square centimeter of skin.
What is UPF?
UPF stands for Ultraviolet Protection Factor and is a standard used in the United States, Australia and New Zealand to rate how much UV radiation is able to penetrate through a specific fabric. The higher the UPF rating, the better the sun protection. For example, if you’re wearing a fishing shirt with a UPF rating of 50, only 1/50th (2%) of the sun’s radiation will pass through. A garment rated UPF 20 permits 1/20th (5%) of UV transmission, and so on. The chart below provides a breakdown of UPF ratings and protection quality:
UPF Rating % of UV Blocked Quality of Protection UPF 15 and 20 93.3 – 95.8% Good UPF 25, 30 and 35 96.0 – 97.4% Very Good UPF 40, 45 and 50+ 97.5 – 98.0% Excellent
In order to meet US ASTM D6544 standards, UPF clothing must also undergo the following before being tested:
- Undergo 40 simulated launderings
- Be exposed to 100 fading units of simulated sunlight
- Exposure to chlorinated water (for swimwear fabrics)
By now, you may be wondering if regular clothing is enough to block UV rays. The answer is tricky. Most clothing blocks some amount of ultraviolet radiation. However, certain fabrics are far more UV resistant than others. Below are some of the primary factors that determine how effective clothing will be at protecting your skin from the sun:
Fiber Type: Natural fibers like cotton, hemp and linen typically offer less UV protection compared to synthetic fabrics like polyester and nylon. High-luster polyesters and satiny silks boost UV protection even further thanks to high reflectivity.
Fabric Density: A fabric’s weave and fiber content directly relate to fabric density, and denser fabric blocks more UV compared to loosely-woven fabric. Although denser fabrics may sound overly warm for the noonday sun, not all dense fabrics are heavy. Some can actually be quite lightweight. Nylon fabric, for example, can be both dense and light.
Fabric Stretch: As you can probably imagine, when fabric gets stretched, the spaces between the weave become larger. This allows more sunlight and UV to pass through. Fabrics that contain elastane (e.g. spandex and Lyra®) have the most “built-in” stretch and offer less UV protection the more they are stretched.
Other Factors: Fabric dyes and treatments also affect UV resistance. Some fabric dyes and pigments block more UV than others. Certain fabric treatments, such as those designed to soften fabric, may alter UV resistance. Fabric condition is another factor. An old, worn-out shirt that’s been washed repeatedly for several years will block less UV compared to when it was new.
Even with these factors in mind, it can be difficult to accurately gauge the amount of UV protection a specific garment will provide, unless that garment carries a UPF rating. To ensure you’re getting the most reliable protection from your apparel, consider choosing UPF-rated clothing. Who needs UPF clothing the most?
- People who live in areas that frequently experience a high UV index, like Australia, where UV-disrupting ozone is significantly depleted
- People with fair skin and people who sunburn easily
- People who spend more than a few hours outside on a regular basis
- People who spend a lot of time around reflective surfaces like water, sand and snow
- People who live or spend time at high altitudes or near the equator
- Infants and children
- Anyone who wants the best possible protection from UV rays
Most people are already aware that protecting exposed skin from direct sunlight is important to avoid sunburn, sun damage and the health risks associated with prolonged sun exposure. For the best results, however, it’s very important to choose a “full spectrum” sunscreen that protects from both UVA and UVB rays. The ideal SPF rating for you depends on several factors, including your own skin’s natural resistance, weather conditions, time of day and other factors.
As we mentioned earlier, SPF ratings apply to how much UV radiation a sunscreen will block when applied sufficiently to exposed skin (about two milligrams per square centimeter of skin). According to the FDA, the SPF rating of sunscreen is not directly related to the duration of UV exposure but rather to the amount of UV exposure. In other words, it’s not just about how long you’re outside. The intensity of solar energy varies throughout the day. For example, one hour of sunlight at 9 a.m. could actually equate to the same amount of solar energy exposure as fifteen minutes of sunlight at 1 p.m., when the sun is at its peak. Basically, if you plan to be out in the sun during the middle of the day, you’ll likely need more protection than you would in the morning or late afternoon.
A person’s complexion is another factor when choosing SPF. Most sunscreen falls within a range of about SPF 4 to SPF 50. If you’re fair-skinned and burn easily, you’ll want to choose a sunblock with a high rating, such as SPF 30 or higher. If you have a naturally darker complexion, you may not need as much protection. Again, conditions like UV index should also be considered when choosing a sun protection factor. Also be aware that spending time around reflective surfaces like sand, water, ice and snow will amplify your UV exposure, requiring additional protection.
Finally, sun protection is extremely important for infants and children. Babies and young children are more susceptible to sunburn than adults, and sunburns early in life can be a contributing factor to cancer risk as an adult. Always protect children when spending time out in the sun.
- Choose a full-spectrum sunscreen that blocks UVA and UVB rays
- Look for proven sun-blocking ingredients like zinc oxide and titanium oxide
- Apply a heavy, even coat of sunscreen 30 minutes prior to sun exposure
- Re-apply every two hours, especially when spending time in the water
- Kids and fair-skinned people should use a higher SPF sunblock
- Be aware of conditions that increase UV exposure, like reflective surfaces (water, snow and sand), high UV index and high altitudes
- If you’re swimming or playing sports, choose a waterproof and sweat-proof sunblock
Your skin isn’t the only thing that needs protection from the sun. Your eyes are equally sensitive to harsh ultraviolet rays. Over time, exposure to UV radiation can eventually cause eye damage, including macular degeneration and possibly even cataracts. In order to safeguard your peepers, it’s a very good idea to choose sunglasses that offer 100% protection from both UVA and UVB rays. If you plan on spending time around reflective surfaces like water, snow, ice or sand, you may consider choosing a pair of sunglasses with polarized lenses to block eye-fatiguing glare. Want more info on buying sunglasses? Be sure to visit our Sunglasses Guide.