This article originally appeared on Time.com.

When it comes to flying, nothing about a close proximity to strangers and bathrooms for hours on end feels particularly clean. And while you may not be able to make the flight shorter or the seats bigger, you can make your experience more sanitary by avoiding some of the dirtiest places on airplanes.

It’s worth noting that some people may be more susceptible to getting sick on planes because the cabin air humidity is under 20%, whereas home humidity is generally over 30%, according to the World Health Organization. The dry air exposure affects mucus, the immune system’s front line of defense, leaving people marginally more vulnerable to getting sick. A 2004 study in the Journal of Environmental Health Research found that people are far more likely — 113 times more, by one of the study’s measures — to catch the common cold during a flight than normal ground transmission.

Humidity aside, there are a handful of especially dirty spots, according to research and advisories from travel physicians. Here’s how to avoid them.

Airplane tray tables

The potentially grimiest place on an airplane unfolds right into your lap.

Alarmingly, a 2015 study by TravelMath that tested samples from hard surfaces in planes found that tray table surfaces had more than eight times the amount of bacteria per square inch than the lavatory flush buttons. The trays had 2,155 colony forming units of bacteria per square inch—compared to the 127 cfu/sq. in., which is what the National Science Foundation says is standard for a toilet seat at home.

Dr. Charles Gerba, microbiologist at the University of Arizona, tells TIME that the trays he’s tested through research have had cold viruses, human parainfluenza viruses, norovirus (which can cause diarrhea and vomiting) and the superbug MRSA, which causes skin infections.

The high amount of bacteria is likely linked to plane cleaning crews not having enough time between flights to wipe down the tray tables, the Wall Street Journal reports. And when they do get clean, those airlines may be using general cleaners instead of disinfectants.

In the meantime, to avoid eating dinner off a tray that someone piled used tissues or changed a baby’s diaper on just hours earlier, wipe it down with a sanitizing wipe, Dr. Michael Zimring, director of travel medicine at Baltimore’s Mercy Medical Center, tells TIME. But if you don’t feel like even touching the table (Gerba does, but Zimring says he doesn’t bother), avoid eating food directly off the surface.

“My food will stay on a paper plate or wrapper,” adds Zimring.

Air vents and seatbelt buckles

Two plane features with frequent usage (that may not receive a regular cleaning) also make the list.

The air vents above each seat are great for circulating ventilated air to each passenger, but the TravelMath testing found 285 CFU/sq…

This article originally appeared on Time.com.

Maybe there’s some science behind the dramatic eyebrow trend after all.

A new study finds that facial features, like lips and eyebrows, tend to stand out less as people get older. Because of that, the authors say, people perceive faces with more contrast as younger.

In the study, published in the journal Frontiers in Psychology, researchers analyzed photographs of 763 makeup-free women with various skin tones between ages 20 and 80. A computer program analyzed the photos for facial contrast: a measure of how much the eyes, lips and eyebrows stand out due to differences in color, lightness or darkness with the surrounding skin.

Younger women had more facial contrast, and older women had less. Contrast especially decreased in areas around the mouth and eyebrows as women got older.

Next, the researchers Photoshopped some of the pictures, creating two nearly identical versions of each face with varying levels of contrast. They showed these photographs to volunteers and asked them to choose the younger-looking face. Almost 80% of the time, people said the high-contrast face appeared younger than the low-contrast one.

The findings were similar across a variety of ethnicities, suggesting that facial contrast—like wrinkles and changes in skin pigmentation—is truly a “cross-cultural cue” for perceiving how old a person is, the authors wrote in their paper.

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Anyone who’s ever filtered a selfie on Instagram won’t be surprised by this effect of contrast. But the findings may also help explain why people often use makeup to look younger.

The study didn’t involve makeup, so the authors say for sure that darkening features cosmetically would have the same anti-aging results as demonstrated in the study. “But the way we manipulated features in the photos was very similar to what you’d do with makeup, and I would be surprised if you couldn’t get similar effects,” says co-author Richard Russell, associate professor of psychology at Gettysburg College. “We know that lips get less red with age and eyebrows get lighter, for instance, and those are both things that you could address with makeup, if you wanted.”

The biggest surprise of all was the power of the brow. For women of all ethnicities, brow color faded with age—so darkening them may really make people look younger, the researchers say.

Though the study was only done in women, the findings likely apply to men, too. Other research suggests that the decline of facial contrast with age is not just true of women, but also true of men.

This article originally appeared on Time.com.

Is there such a thing as too much exercise?

A new study, published in the journal Mayo Clinic Proceedings, suggests that there is. Fitness diehards may have a higher-than-average risk of coronary artery calcification (CAC): a buildup of calcium in the artery walls of the heart that makes arteries less flexible and is often a harbinger of heart disease. But the vast majority of people, experts say, don’t need to worry about overdoing it.

A team of researchers, led by scientists from the University of Illinois and Kaiser Permanente, tracked the exercise habits of more than 3,000 people over 25 years. People were split into three groups based on whether they met the national physical activity guidelines (which call for 150 minutes of exercise per week), failed to reach them or exceeded them.

Surprisingly, compared to people who exercised moderately, those who hit the gym for longer than 7.5 hours per week—three times more than guidelines call for—had a 27% higher risk of developing CAC by middle age. White men in that category were particularly at risk; they had an 86% higher chance of CAC. About 40% of people who exercised the most developed any amount of calcification after 25 years.

The results may seem like a reason to eschew your evening workout. But exercise is generally good—not bad—for the heart, and people typically need more of it—not less.

“This [study] doesn’t apply to 99% of people,” says Dr. Deepak Bhatt, executive director of interventional cardiovascular services at Brigham and Women’s Hospital in Boston. “Most people are not getting into this range of exercise. The problem in the U.S. is the exact opposite, that most people are getting nowhere near the recommended amount of exercise.”

Even if hardcore exercisers do have more calcium buildup, it’s still not clear if that’s damaging the heart, says Dr. Aaron Baggish, director of the cardiovascular performance program at Massachusetts General Hospital. While the results are intriguing, the study doesn’t actually show that people with a heightened risk of CAC went on to have heart attacks or other health problems, Baggish says, and that means it’s too soon to say whether extreme exercise is actually causing heart issues.

While doctors know that calcium buildup in the hearts of sedentary people is a bad sign, Baggish says it’s not clear whether that’s true of very active people, too. The body deploys calcium to repair injuries and inflammation, so marathon runners, endurance athletes and other regular exercisers may accumulate calcium as the body recovers from stress, he says—but that doesn’t necessarily mean it’s causing problems.

“Think about arthritis in your knee,” Baggish says. “If you are active, fit and healthy, you are much more likely to have good knee function later in life than if you sit around and you’re overweight and unhealthy…