Skin wounds and burns heal fastest if they occur during the day

Humanity's reduced body hair slows down wound healing

Cuts to human skin take twice as long to heal compared to chimps and other mammals. Scientists argue this is due to the reduced number of hair follicles on human bodies. Hair follicles contain stem cells which help repair skin cells faster, so as humanity shed its hair over time, so to speak, it also slowed its wound healing.

Heart attacks are less harmful at night

When heart attacks occur during the day they typically do more harm to the heart tissue than if they occur at night. A 2025 study suggests that daytime heart attacks have higher levels of immune cells called neutrophils to contend with and they appear to worsen the injury. Scientists confirmed this same pattern in experiments with mice. (Some readers may experience a paywall.)

NASA began investigating the healing properties of red light therapy in the 1980s, when researchers studying how LED lights could aid in photosynthesis noticed that their hands seemed to heal faster than normal under the lights.

Studies suggest when you sleep is as important as how much you get.

World records are often broken later in the day—and scientists wonder if muscle clocks explain the difference.

Firework or sparkler burns can have large effects on our hands' range of motion.

There is a best way to wake up—but not a best time

Sleep and circadian rhythm researchers say that waking up at a consistent time each day—even on weekends—and viewing morning sunlight are the best ways to keep body functions running at their peak. (Some users may encounter a paywall.)

Antiperspirants work better if they are applied at night

Dermatologists recommend applying antiperspirant at night for the best results. When applied to clean, dry skin at night, the active ingredient in most antiperspirants (aluminum salt), combined with the skin's natural moisture, forms plugs that block sweat glands, limiting sweat and related odors.

Laser skin treatments can promote the production of collagen

Skin resurfacing vaporizes the top layer of skin to reveal healthier, new skin, while collagen can give the skin structure and elasticity. Such procedures treat scars and burns, but may leave light spots on the skin.

Why Friday surgeries are (likely) riskier

Scheduling surgery on a Friday may lead to more complications—up to 5% more often—compared to surgeries performed after the weekend. The research was conducted by a team from the United States and Canada and analyzed data from over 450,000 patients who underwent common surgeries in Ontario between 2007 and 2019. Check out their findings here.

Red light therapy—a treatment harnessing a specific form of energy that penetrates the top layers of skin—is marketed for skincare and wellness, but has its roots in NASA plant growth research.

See images of medical cases of firework injuries shared on this 'Instagram for doctors.' (Warning: Graphic images.)

The design of a psychiatric ward in Norway aims to integrate more circadian rhythm-friendly lights as part of its treatment protocols for conditions including psychosis, severe depression, and more.

Certain vaccinations may be more effective when given around the middle of the day.

Prehistoric hunter-gatherers performed amputations and appear to have provided post-op care, according to analysis of a recent fossil discovery from almost 31,000 years ago.

There is a template for how to live a better, healthier day, and it includes a digital sunset

Science suggests that early-morning exercise, later-morning peak work or social time, consistent exercise, and a "digital sunset"—starting to turn down the lights in the evening and avoid screens—are important for circadian health.

Social jetlag—differing weekend and weekday schedules—is physiologically similar to jet lag

Recovering from schedules that drastically differ between weekends and weekdays, something that was first described in academic work in 2006, is a growing concern in public health as more research shows that consistent daily routines are important for human health.

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak annually.

This 1440 Original video dives into what the science says about phototherapy and its various potential applications.

High-powered red light therapy—delivered directly to nerve fibers via a fiber optic needle—has been used in recent experimental research to suppress pain.

Urushiol, the oily toxin in poison ivy, can remain allergenic on clothing for up to 5 years—or even longer.

Ending daylight saving time may prevent as many as 300,000 strokes annually

Changing clocks twice a year disrupts circadian rhythms, which last an average of 24 hours and 12 minutes. Studies have shown that permanent daylight saving time provides fewer health benefits than standard time.

Artificial lighting and modern practices like working late are linked with sleep shifts

An analysis of five adults participating in a German reality program that tasked them with living in a Stone-Age-like settlement for 2.5 months, provided some insights into how modern conditions may have shifted our circadian rhythms. The participants slept about 90 minutes more under these conditions, and went to bed earlier and rose earlier, raising questions about how circadian rhythms, sleep, and sleep quality are affected by modern lifestyles.

Daylight Saving Time is linked to a rise in heart attacks and strokes

Losing an hour of sleep with seasonal time changes is not good for our health and it’s linked to risks for the first couple days of Daylight Saving Time, including a short-term rise in heart attacks and strokes. Scientists theorize these elevated risks are linked to the disruption to the body’s circadian rhythm.

Beyond burns, fireworks can harm respiratory, auditory, and visual health.

Certain visible light therapies, when applied at specific intensities, can be used to treat skin conditions, including acne.

Being struck by lightning has a mortality rate of about 10%

Near-immediate deaths are the result of electrical disruptions in the heart and nervous system, causing cardiac arrest, but severe skin burns, temporary paralysis, and blown eardrums are more common. About 74% of survivors are left with a long-term disability, which includes brain damage and changes in memory and mood.

Wind chill speeds up the loss of heat from the body

During cold weather conditions, strong winds against exposed skin can produce a sensation of temperature colder than the surrounding air temperature. The accelerated loss of body heat increases the risk of frostbite and hypothermia, with frostbite able to set in as quickly as five minutes.

Most things you would get tested for at the doctor’s office are influenced by circadian rhythm

In this video, a Salk Institute Researcher offers daily habit tips focused on aligning with your circadian rhythms. She notes heart rate and blood pressure are highest in the afternoon, for example, and there’s a triglyceride peak in the morning. Generally, she says, it’s a good idea to schedule your doctor’s checkups at the same time of day each year so there’s consistency across your data.

Forty to 110 minutes of deep sleep is recommended per night

Adults typically spend 10% to 20% of the night in deep sleep, also known as slow-wave sleep, with the rest of the night spent either in light sleep or REM states.

Research advances suggest death takes much longer than we realized

Recent research indicates that organs, including the brain, are better at handling a lack of oxygen after the heart stops beating than previously known. Such findings may open up possibilities that include someday reversing certain death processes and expanding the availability of organs available for organ donations. (Some users may experience a paywall.)

Cold-blooded reptiles seek heat, and that behavior may help combat fungal infections

This Radiolab podcast episode takes on the idea that though our human bodies are too warm for the majority of fungal species to effectively replicate inside our bodies, that's not the case for reptiles. Yet when those species warm their bodies by basking in the sun on rocks, they can soak up heat and may also help keep fungal infections in check.

Self-care can't fix burnout on its own

Steps such as exercise, breathing, mindful eating, and spending time with friends, can help alleviate the fight-or-flight mode response of the body to alleviate stress, but they don't fix the stressors causing the burnout. To address those, workplaces may need to consider how to better manage workloads and duties.

The immune system fights tattoos

Our skin is a fascinating organ that wants nothing more than to protect our bodies from the outside world. Tattoos penetrate that protective wall to inject ink directly into the sensitive, immunologically rich layer of skin known as the dermis.

The side effects of falling back and springing forward

Daylight saving time can interfere with a person’s sleep schedule, but it also has been linked to increased rates of depression, heart attack, stroke, cancer, and car accidents. UT Southwestern’s Dr. Joseph Takahashi explains why the time change is bad for your brain and health.

Surgery before the dawn of anesthesia

The arc toward anesthetics was painfully slow, with early pain mitigation offerings ranging from analgesics—drugs that dim pain but don't block it—and numbing surgical sites with cold water to gassing patients with carbon dioxide or bashing or bleeding them unconscious. Such treatments and the torturous surgery they preceded led many to avoid even life-saving procedures, and those who survived often kept silent about the trauma.

Staying on standard time permanently would slightly reduce obesity and stroke risk

A 2025 study that examined time changes found that permanently changing to standard time would slightly reduce obesity and stroke risk more than switching to permanent daylight saving time.

Heat-related complications are of greater concern for distance runners than cardiac threats

Analysis of more than 130,000 runners in Tel Aviv events during a seven-year period indicated that the runners were 10 times more likely to experience heatstroke than serious cardiac problems. Scientists suggest that runners should take 10 to 14 days to acclimate to a hot climate before tackling a serious run.

In 2026, the US FDA approved a light-activated gel combined with red light therapy as a nonsurgical treatment option for the most common type of skin cancer.

Limb regeneration research may lead to treatments for arthritis

For scientists pursuing the cure for arthritis, the holy grail of discoveries lies in how to regrow healthy cartilage inside human joints. While this feat has so far resisted our best scientific attempts, there are plenty of other human tissues—such as the liver and fingertips—that will successfully regenerate.

The body can remove tattoos after they are broken down by laser

Tattoos place blobs of ink below the surface layers of the skin in packets too large for white blood cells to clear out. By breaking the ink into smaller pieces, they can be processed by the immune system, which is responsible for removing foreign matter.

A 1974 Science News article proclaimed that within a decade, light therapy would be on par with traditional drugs.

11 people died from firework injuries in the US in 2024, with most of those deaths involving misuse of the explosives and device malfunctions or misfires.

How dreams affect your memory

In 1999, scientists conducted a study in which participants were asked to recall images flashed before them for milliseconds. They found that participants who slept before recalling the information performed better than those who had been asked to recall the same information that same day. This was some of the earliest convincing evidence of how crucial sleep is for learning and memory, findings that current research continues to strengthen.

Organ donation isn't usually logistically possible if you die at home

Since organs need to be well-preserved for organ donation, with oxygen flowing through the body, internal organs often aren't viable for organ donation if someone dies at home. But some tissues—like eye corneas and skin tissue—may still be donated since they remain usable for a longer period without oxygen flow.

Circadian rhythms shift as we age—making older adults want to go to bed earlier

Throughout our lives our internal biological clocks shift. Early-to-rise toddlers become hard-to-wake teens and eventually early-to-sleep seniors. Circadian rhythm fluctuations throughout our life cycle explain some of these changes.

Heart attack risk jumps to 21 times its norm on the day of a loved one's death

Research published in 2012 suggests that the intense emotional burden of suffering a loved one's death can escalate heart rate, blood pressure, and clot risks—culminating in elevated heart attack risk. The increased heart attack risk remains after that first day, remaining eight times above normal during the first week, and then dropping down over the course of a month. (Some users may encounter a paywall.)

Unlike America's recommendations, Australian authorities don't encourage routine sunscreen use for darker skin tones—reasoning that melanoma risk is low, and it's better to get UV exposure to help the body naturally produce vitamin D.

The average cell's DNA is damaged thousands of times daily

In the case of radiation-induced distortions in a DNA strand, specialized proteins can cut out entire segments and rebuild them using the second strand as a complementary template. If both DNA strands are completely severed, proteins interlace undamaged DNA with the severed DNA and rebuild both using complementary base pairing.

Ticks must typically be attached to a person for more than 24 hours to transmit Lyme

Infected blacklegged ticks must typically be attached to a person for more than 24 hours—and often closer to 36—to transmit Lyme. That period is enough time for the bacteria that causes Lyme to migrate from the tick's gut into the person's bloodstream while it's latched on through its bite. (There are rare documented cases of transmission under 24 hours.) Rapid removal of the tick is key to disease prevention.