Too Hot to Handle?
Emory experts address your concerns about heatstroke, hydration, and staying healthy as temperatures soar and summers get longer
We are deep into summer and here are some things you need to know.
How sunscreens work
Excessive ultraviolet radiation can damage your skin. Here’s how sunscreen helps protect it.
Climate change is bringing the heat
The ways climate change and heat affect our lives and ways to move toward a cooler world.
Staying safer in the summer
This ER doctor hopes not to see you (but will if you need her).
EDITOR'S NOTE
As temperatures climb, I am not prepared. I grew up in Florida, so I’m no stranger to burning your hands on your car’s molten steering wheel, but each summer feels more brutal than the last.
Is the sun really getting hotter? Why are there so many different types of sunscreens? Is climate change impacting summer weather? And where is an oscillating sprinkler when I need one?
Below, we share the insights of Emory experts, from ethnobotanists to dermatologists to public health experts to ER docs, on ways to stay cool and healthy as those rays beat down upon our heads (which, they say, should definitely be covered by a hat when outside!)
And me? I’ve decided to walk slower, wear light-colored, breathable fabrics, take my sunhat everywhere (a decision compounded by my dermatologist taking a snip from my scalp just last week for analysis), join the coconut water craze, invest in a quality pair of shades, and find out if I still fit on a Wham-O Slip ’n’ Slide.
Mary Loftus, Editor, Emory Health Digest
How Does Sunscreen Work?
By CASSANDRA QUAVE
Good morning from the (very!) hot Mediterranean. I’m writing today from my in-laws’ house in the Basilicata province of southern Italy, and am here on vacation to visit family after a series of conferences on ethnobotany and plant metabolic engineering in Europe.
Southern Europe is experiencing a major heat wave, with temperatures of 114 F reported in Spain. In the sweltering heat, the first thing I want to do is cool off in the sea or a pool. But that comes with risks, too: namely, ultraviolet radiation (UVR)-induced skin damage.
I’m no stranger to the heat or sunburns. I’m fair-skinned and grew up in South Florida during the ’80s and ’90s, when it was trendy to slather on tanning oil and bask on lawn chairs in pursuit of a deep tan. Excessive UVR exposure can not only cause sunburns but also damage the skin, causing photoaging, pigmentary disorders and an increased risk for skin cancers.
These days, I no longer chase that deep tan. Instead, I cover up as much as possible with a long-sleeved photoprotective shirt, a wide-brimmed hat, sunscreen, and by seeking out the shade. In today’s post, I’ll share a bit about how UVR damages the skin and how sunscreen can offer some protection.
What is UVR?
Ultraviolet radiation (UVR) is a component of sunlight that includes UVB (290–320 nanometer) and UVA (320–400 nanometer) wavelengths. UVB is the primary cause of sunburn and plays a major role in the development of skin cancer, while UVA—especially the longer UVA1 rays—contributes to photoaging, pigmentary disorders, and skin cancers. UVA also penetrates deeper into the skin and remains relatively constant year-round.
What is sunscreen?
Sunscreen is a topical product designed to protect the skin from UVR-induced damage. It contains active ingredients that either absorb or reflect harmful UV rays, and may include additives like antioxidants and iron oxides to broaden protection, especially against visible light, which can contribute to pigmentation issues. Sunscreens come in various formulations (e.g., lotions, sprays, sticks, and more) tailored to user preferences and skin types.
How does sunscreen work?
Sunscreen works by incorporating UV filters—either organic (chemical) or inorganic (physical/mineral)—that absorb, and to a lesser extent, reflect and scatter UVR. Organic filters convert UV energy into heat through their chemical structure. Inorganic filters like zinc oxide and titanium dioxide also absorb UVR, though they were once thought to act mostly by reflection. Modern formulations combine ingredients to provide broad-spectrum protection across the UVB, UVA, and even visible light ranges.
- Ingredients that absorb UVR: Organic (chemical) filters absorb UVR and convert it into harmless heat. Examples include avobenzone (for UVA1 and UVA2), octinoxate, oxybenzone, octocrylene, and homosalate (primarily for UVB). These ingredients absorb specific wavelengths of UV light efficiently.
- Ingredients that scatter and reflect light: Inorganic (physical) filters such as zinc oxide and titanium dioxide scatter and reflect a small portion of UVR, but primarily absorb it. Micronized or nanoparticle forms reduce the white, chalky appearance on the skin, improving cosmetic appeal while maintaining protection. Larger pigmentary particles, especially those in tinted formulations, can enhance visible light protection through greater light scattering.
What about SPF?
You’ll notice the SPF number prominently displayed on sunscreen products, but what does this number mean? The SPF, or Sun Protection Factor, is a measure of how well a sunscreen protects the skin from UVB radiation, the type of ultraviolet light primarily responsible for sunburn.
In simple terms, SPF tells you how much longer you can stay in the sun without burning compared to not wearing any sunscreen. For example, SPF 30 means it would take 30 times longer to develop sunburn than if you had no protection—assuming the product is applied correctly and generously.
In real-world conditions, most people apply much less sunscreen than the recommended amount. As a result, the actual protection may be significantly lower than what’s on the label. Studies have shown that SPF 30 applied at a quarter of the recommended thickness can offer as little as SPF 9 in practice. That’s why choosing a higher SPF (like 50 or more) can provide a more reliable buffer, especially when application is imperfect.
The takeaway
UV radiation is a powerful hazard that damages the skin in multiple ways—from sunburn and photoaging to pigment disorders and cancer. The first lines of defense are physical barriers such as skin protective clothing, hat, and seeking shade. Beyond these measures, sunscreen remains a cornerstone of photoprotection. For best results, choose a broad-spectrum product with SPF 30 or higher (I use SPF 50 or 70), apply it generously and reapply regularly. Consider tinted or antioxidant-enriched formulations for added benefits, especially for individuals with skin of color or sensitivity to visible light.
Emory ethnobotanist Cassandra Quave is herbarium director at the School of Medicine, a Guggenheim Fellow, a CNN Champion for Change, and a fellow of the National Academy of Inventors. She authored a memoir, The Plant Hunter, hosts the Foodie Pharmacology podcast, and writes the Nature’s Pharmacy newsletter, where this essay first appeared. Read Quave’s next newsletter to learn which herbs can soothe sunburned skin.
SHORT SHORTS
As the daughter of farmworkers in El Salvador, nurse-scientist Roxana Chicas seeks to improve the health of underserved and vulnerable Latinx communities, particularly agricultural workers. Using real-time biomonitoring, Chicas conducted the first field-based intervention study examining ways to reduce core body temperature and improve health among farmworkers in the US.
Roxana Chicas, assistant professor at Emory’s Nell Hodgson Woodruff School of Nursing.
“...Beloved bright voices of summer echoing like the ice cream man in his whirring truck...”
IN THE PRESS
Catching the (Heat) Wave
A conversation with heat wave researcher Daniel Smith, adjunct faculty at Emory’s Nell Hodgson Woodruff School of Nursing, who works with the school’s Farmworker Family Health Program each summer. “I grew up on a dairy farm in North Carolina,” Smith says. “Farmers are always worried about weather conditions—if it’s raining, too hot, too cold, too windy. That was my life, understanding the connection between humans and the environment.”
Smith takes on a few summer heat topics, below.
Is it just me, or are summers getting hotter and longer?
Last year was the hottest year globally since record-keeping began in the 1800s, and the first half of 2025 has been record-breaking as well.
For many areas, it’s the humidity and the scorching temperatures that make it feel so hot. “The heat index is both the temperature and the humidity, because 90 degrees with 85 percent humidity is vastly different than 90 degrees with 10 percent humidity,” Smith says. “Until we get the heat index on people’s phones like the air quality index, we’ve really got to be listening to our bodies.”
What will our bodies tell us?
Muscle cramping, heavy sweating, shortness of breath, dizziness, headaches, nausea—dehydration and heat exhaustion can take many forms. Discolored urine, for instance, is often an early sign that someone is not well-hydrated. “We have to teach people those warning signs of the body so that they can then listen and say, ‘OK, I’m getting too hot. I need to drink water. I need to drink an electrolyte solution,’ ” he says.
Untreated dehydration and heat exhaustion can worsen into heatstroke. “If we think about heat-related illness as a spectrum, the more dangerous parts of the spectrum are where you’re becoming confused,” Smith says. “Your heart rate starts to increase. You’re ultimately becoming dehydrated and your blood pressure is falling, which then can lead to the next part of the spectrum, which is heatstroke.”
Heatstroke is the most serious heat-related illness, capable of causing permanent disability or death if untreated.
What do I do if I feel dehydrated?
Don’t grab your favorite sports drink, says Smith. “For dehydration, the first thing is to just drink water,” he says. “You want cold water.” He also recommends, if you’re outside, a balanced hydration solution such as electrolyte tablets or packets, with healthy salt balances.
Another important step is to find a way to cool down: quickly. “The biggest myth is that you should cool yourself slowly,” he says. “You want that cooling effect to be rapid.” He suggests getting inside immediately to somewhere with air conditioning or taking a dip in a pool or a cold shower. “If you have cooling towels, the places on your body to apply them are the back of the neck, under the arms and on the groin, because that’s where our body naturally releases its heat,” he says.
Finally, plan your time outside for morning or evening, not during the heat of the day. “If you’re going to be outside working in your yard or going on a run, do it at the beginning or end of the day, when it’s a little cooler,” he says. It’s best to plan outdoor activities before 10 a.m. and after 5 p.m.
This article first appeared in the AJC and has been edited for this package.
Daniel Smith, adjunct faculty member at Emory’s Nell Hodgson Woodruff School of Nursing.
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For More Information |
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For more information on how to identify and treat heatstroke, heat exhaustion, heat cramps, sunburn and heat rash, visit cdc.gov for its heat-related illness fact sheet. To know your community’s current heat index, visit weather.gov and type your information into the search bar. |
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4 Qs: A Dermatologist on Coping with the Rays
Dr. Jordan Lim is a dual board-certified dermatologist/Mohs micrographic surgeon and assistant professor of dermatology at Emory School of Medicine. Mohs surgery is a specialized surgical technique used to treat skin cancer. It involves the precise removal of cancerous tissue layer by layer, with each layer examined under a microscope until all cancerous cells are eliminated.
“I’m originally from Northern Canada where summers are short and sacred,” she says. “Growing up with limited summer days, I spent every moment possible outdoors. Since childhood, sun safety has been vital to ensuring nothing got in the way of enjoying those few sweet summer weeks!”
Why is the sun harmful?
The sun’s UV rays can cause damage to the skin leading to the development of skin cancer and premature aging. Approximately 1 in 5 in the US will develop skin cancer in their lifetime.
Do we only have to protect our skin on sunny days?
Believe it or not, the sun’s UV rays penetrate through the clouds and are present year round, regardless of the season or weather. The easiest way to protect your skin is to make sun safe behaviors part of your daily routine. If that doesn't suit your lifestyle, consider checking the UV index and avoiding the peak UV times of the day (between 10 a.m. and 2 p.m.)
What kind of sunscreen should I be using?
The most effective sunscreen is one with an SPF of 30 or higher that provides broad spectrum protection (which means it prevents both the sun’s UVA and UVB rays from damaging the skin). You need to reapply every two hours. Sensitive skin? Look for a mineral or physical sunscreen. Trying to prevent dark spots? Get a tinted mineral or physical sunscreen.
Will anything other than sunscreen protect my skin?
- Wear a wide-brimmed hat that not only protects your scalp and face but also your ears and neck.
- Seek shade whenever you’re outside for a prolonged amount of time.
- Wear clothing with a UPF (Ultraviolet Protection Factor) number. This is like having sunscreen built into your clothing. UPF is in a variety of clothes, from dress shirts to athletic wear.
SHORT SHORTS
Beware of Snake Bites as Temperatures Rise
Snakes are cold blooded, which is why they spend a lot of time basking in the sun. Emory researchers have found, in fact, that the risk of being bitten by a snake increases 6 percent for every degree Celsius daily temperatures increase. “This is certainly higher than we often see from other types of health outcomes linked to heat,” says the study’s lead author Noah Scovronick, assistant professor of environmental health at Emory’s Rollins School of Public Health.
“Summer seemed to bloom against the will
of the sun, which news reports claimed flamed hotter
on this planet than when our dead fathers
wiped sweat from their necks.”
PODCAST
Extreme Heat: It’s getting hot out there
The topic: Climate change is bringing the heat and, along with it, volatile weather events and health hazards. On this episode of Health Wanted, host Laurel Bristow hones in on the ways climate change and heat affect our lives. Her guest, Noah Scovronick, assistant professor at Emory’s Rollins School of Public Health, offers his perspective regarding climate research and ways to move toward a cooler world.
Laurel Bristow, an infectious disease expert and research scientist, is the associate director of audience development at Emory’s Rollins School of Public Health and host of the podcast Health Wanted.
Staying out of the ER
With summer comes sunny days, family cookouts and swimming pools—and the possibility of unexpected injuries from extreme heat and outdoor activities.
“Typically, in the main emergency department, you’re going to see heart attacks, strokes, people with collapsed lungs and difficulty breathing,” says Sofia Khan, MD, who practices emergency medicine at Emory Decatur Hospital.
Summer brings more “secondary injuries,” caused by environmental factors such as dehydration or swimming.
Dehydration is more common when people spend more time outside, and it’s a risk that especially affects older people. “They don’t have the same reserve when it comes to hydration,” Khan says. Outdoor activity can cause them to become severely dehydrated, leading to disorientation and confusion. Learn more about symptoms of dehydration and heat exhaustion.
Swimming means more patients visit the emergency department who have breathed in water. There can be aftereffects from near-drowning. For instance, “some of the water gets in their lungs instead of their stomach, so they can develop a pneumonia,” says Khan.
Khan has a few tips for staying safer during summer activities:
- Take cooling breaks. “If you’re at a barbecue, spend about 5 or 10 minutes inside so your body has some time out of the heat,” Khan says. “If you’re at the pool, get in. And hydration is really important.”
- Find the shady spot. “The shade is usually about 10 degrees cooler,” Khan says. “You won’t perspire as much, which doesn’t lead to as much dehydration.”
- Hydrate. In addition to drinking water, think about increasing your water intake with healthy summer foods. “Fruits and vegetables have a lot of water content in them,” she says, so grab that slice of watermelon.
- Drink responsibly. “I usually tell people there should be one adult who’s not drinking,” says Khan. “You may not necessarily be intoxicated but your inhibition and guard are down so you’re more likely to say yes to kids when you shouldn’t.”
- Keep a first aid kit nearby. “Pack that along with your cooler of ice and drinks,” Khan says. Make sure to add sunscreen and bug spray to your kit.
SHORT SHORTS
Summer is vacation season. Emory epidemiologist Jodie Guest shares six tips for healthier summer travel, including this one: Vector-borne diseases are in season in many areas across the country. Wearing long sleeves and using insect repellant can help you avoid bites.
Jodie Guest is a professor of epidemiology, Rollins School of Public Health
Don’t forget Emory’s Travel Well Center if you are traveling internationally. It’s important that you are up to date on vaccinations and knowledgeable about travel-related health concerns.
“I think by now the river must be thick with salmon. Late August, I imagine it as it was that morning: drizzle needling the surface, mist at the banks like a net settling around us—everything damp and shining.”
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