TIME Research

You Asked: Why Is My Scalp So Itchy?

Illustration by Peter Oumanski for TIME

It’s probably dandruff. But everything you’ve heard about dandruff is wrong.

Itches are inscrutable. They arrive unannounced and recede at the rake of a fingernail. But the stubborn kind—the type that skittle across your scalp with terrible regularity—tend to have an easily identifiable cause: Dandruff.

“People think dandruff has to do with dry skin, but it’s actually a problem with how the skin cells on your scalp turn over or replace themselves,” says Dr. Adam Friedman, director of dermatologic research at the Albert Einstein College of Medicine in New York. Your skin is constantly shedding layers of cells while manufacturing new ones, and Friedman says this process can be touchy. “Producing too many cells too quickly can lead to a build-up of dead skin, and this build-up itches and flakes off,” he explains. “That’s dandruff.”

What causes this over-production of skin cells? Anything that puts stress on your immune system—from cold winter temperatures to a crazy week at the office—can switch on certain genetic proteins that speed up the production of skin cells, Friedman says. (Other skin conditions—acne, eczema—also flare up when you’re stressed.)

Yeast microorganisms living on your scalp can also mess with your skin’s cell reproduction, says Dr. Anthony Rossi, a dermatologist with Memorial Sloan Kettering Cancer Center. While usually harmless, these organisms—which live on everyone’s skin—can cause a reaction in some that leads to cell overabundance.

How do you stop the itching and flaking? Dandruff shampoo is a good start. Friedman says these shampoos work by killing scalp microorganisms and turning off the proteins that cause your skin cells to go nuts. That said, shampoos only help if you use them properly. “You’re trying to treat your scalp, so working these into your hair doesn’t do much good,” Friedman says. “You need to massage these products onto your scalp skin and leave them there for a couple minutes before rinsing.” (They aren’t usually very kind to your hair, though.)

He says dandruff shampoos typically include any one of a small number of chemicals that are all pretty much equally effective. While you could wash with them every day without over-drying your scalp, Friedman says this isn’t necessary. “Two or three times a week is plenty,” he says. “And if you don’t see improvement after a few weeks, switching to another product or using them more probably won’t do any good.”

There are many more explanations for an itchy dome. If your scalp is inflamed, red, and itchy, that may be seborrheic dermatitis—a more severe form of dandruff. “Scalp psoriasis is probably the next most common,” Friedman says. It can be hard to tell the difference between the two. But usually the flakes or “plates” of silvery gray plaques associated with scalp psoriasis are larger than dandruff flakes and tougher to brush from your clothing, he says. Scalp psoriasis could also cause some ear or face flaking.

Friedman mentions a few less-common issues: a skin disease called discoid lupus, or an allergic reaction. Rossi says an irritation to hair products like sprays or pomades is another possible itch-instigators. But trying to distinguish between those things and dandruff is really tough, Friedman says.

A good rule of thumb: If you have a red, itchy head and dandruff shampoos aren’t working after a month, see a doctor, he advises. He also cautions against waiting too long if dandruff shampoos don’t get the job done. “If you don’t treat inflammation of the scalp, there’s a chance of skin damage or hair loss,” Friedman says. “There’s often no coming back from that once it happens.”

TIME

You Asked: Why Does My Eye Twitch?

Illustration by Peter Oumanski for TIME

Your eye spasms, decoded

Little lid spasms are common, but they can sometimes be a sign of trouble.

A slight tremor of the eyelid—the type that shows up without warning but scrams just as suddenly—is usually no cause for concern, explains Dr. Wayne Cornblath, a professor of ophthalmology at the University of Michigan’s Kellogg Eye Center. “I think everybody has these once in a while,” Cornblath says. “You rub it, and it eventually stops.”

He’s talking about the kind of whispery muscle spasm that happens in one eyelid (or just a portion of the lid, to be precise). It can be a nuisance, but it usually goes away on its own within a few days, if not a few minutes.

To get rid of eye twitches, you might want to cut back on the caffeine. Too much of it seems to be a trigger, says Cornblath. While the exact mechanisms are a bit of a mystery, research from York University in Canada has shown that caffeine prompts the release of excitatory neurotransmitters like serotonin and noradrenaline. “Caffeine is a stimulant, and it increases reactivity within the muscles and nerves,” Cornblath explains. That may go some way toward explaining how caffeine causes occasional bouts of eyelid quivering, he says.

Getting too little sleep also seems to have an effect, though the reasons why are less clear. “Research has shown a correlation, and we know that getting more sleep can help, but we don’t know why,” Cornblath says. The same can be said for muscle spasms in general, which are quite common but confound explanation. “You hear about low potassium or dehydration, but there doesn’t seem to be much hard evidence,” Cornblath says.

Stress may also play a role, says Dr. Rebecca Taylor, a clinical spokesperson for the American Academy of Ophthalmology. When you’re frazzled, you produce more epinephrine—a fight-of-flight molecule that primes your body for action. This heightened state of muscle arousal may manifest itself in small contractions or spasms, like the one in your eyelid, Taylor says.

In rare cases, when people address these sleep and stress issues and the twitch persists, Cornblath says a single treatment of Botox resolves the problem. Botox temporarily “shuts off” the connection between muscles and nerves, he explains.

Eyelid spasms are usually benign. But that’s not necessarily the case if the twitch spreads, Cornblath and Taylor both say. “If you’re experiencing spasms lower in your face or neck, that’s another story,” Cornblath says.

It’s not as common, but having a spasm in one side of your face—hemifacial spasm—is definitely something to talk to a doctor about, Taylor says. So is another condition, called a bletharospasm, where the whole eyelid closes or blinks involuntarily. There are a handful of potential explanations for both of them, and an eye doctor can help you figure out what’s going on, she recommends.

Back to that irksome little lid twitch: if it lasts for months, get it checked out. But in most cases, it’ll be gone in the blink of an eye.

Read next: Why Am I Cold All The Time?

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TIME Social Networking

You Asked: What Is Yik Yak?

Yik Yak
Mandel Ngan—AFP/Getty Images Yik Yak in the Google Play store.

This anonymous social media network is taking over college campuses

If you’re an early Facebook user like me, you remember when the site required that you had a college-supplied email address. For many users, those were the site’s glory days, a time when parents weren’t airing embarrassing throwback Thursday photos, people could post (nearly) anything they wanted, and there weren’t updates about the mundane nature of cubicle life.

This is the magic that new social network Yik Yak is trying to emulate, and so far, it has largely been a success.

A mobile, anonymous social network with apps for Android and iOS, Yik Yak launched in November 2013 and has been as hot as happy hour on college campuses ever since. “You can think of it as a local, anonymous Twitter or a local virtual bulletin board,” says co-founder Tyler Droll, who started the site with friend and fellow 2013 Furman University graduate Brooks Buffington.

On Yik Yak, users make text posts, also called “yaks,” that can be up- or down-voted by other “yakkers.” These votes help rank each yak: the higher the score, the more popular the post. Yaks can also be commented on, turning the posts into conversation threads. Every post or comment on the network is anonymous — users don’t even get a photo or avatar to distinguish themselves.

Buffington and Droll originally launched the network on their alma mater’s Greenville, South Carolina campus before it quickly spread to other schools. “People started sharing it at various spring break locations,” says Droll of the network’s 2014 surge. “We probably ended the spring semester at around 200 or 300 campuses.” Over the following summer, Yik Yak got even more popular, with college students heading home and telling all their high school friends about it. At one point in the fall, says Buffington, Yik Yak was effectively tied with Facebook for the amount of downloads.

Today Yik Yak is available on around 1,500 college campuses. “We’re starting to get a pretty good foothold into other English-speaking countries like Canada, the U.K. and Australia,” says Buffington.

The bathroom wall

One problem for the service is that it’s being used where it’s not supposed to be — namely, at high schools. “I hate Yik Yak, but I can’t quit Yik Yak,” bemoans my 16-year-old niece. The site’s trash-talking nature is what she dislikes most, but she says she can’t quit it because she feels like she’ll be missing out on conversations her friends and classmates are having. In that way, Yaks can also be like a nasty note scrawled on the bathroom wall. One person wrote it, some people are talking about it, but everyone saw it.

Anonymous social networks can be especially perilous for younger users, because they can be a hive of cyberbullying, racist barbs and hate speech. For instance, in an online petition signed by more than 78,000 people calling for the app to be shut down, one former Yik Yak user outlined how she was encouraged to commit suicide by other anonymous people using the app.

Yik Yak has made efforts to keep younger users off the site by geofencing off grade school campuses in each country it operates, effectively blocking the service from being used in those locations. But once kids leave school grounds, they’re able to open the app — and that’s where parents need to step in and help their children make safe choices on the Internet.

“We try to keep anyone who’s not college age or older off the app, just because the way our app is set up it requires a certain level of maturity,” says Buffington. “Right now I’d say at least 95%, if not more, of our users are college-age kids.”

And while Yik Yak is artificially tethered to college campuses, the app gives anyone the ability to peek at the local buzz, especially if they use it in a dense, urban area where several colleges overlap. Or to check out what the conversation is on a particular campus, Yik Yak’s “peek” feature lets users browse yaks at schools worldwide. It’s a great way to reconnect with your old college. For instance, I wasn’t surprised to see Syracuse University students are still complaining about the epic staircase leading to the dorms on “The Mount.” Or you can use it to see the unfiltered reaction to news emanating from campuses worldwide. For example, someone from Dartmouth College recently posted, “If your [sic] going to ban hard liquor, have the decency to put a Chipotle in town.”

While a great many of its posts are about sex, booze, and syllabi, Yik Yak can also be a great tool for those looking to connect to their community, whether that’s through getting support for LGBTQ issues (yaks about coming out are generally met with encouragement, and the few disparaging comments are generally attacked themselves) or even addressing safety concerns.

“We’ve seen campus alert systems brake, and they used Yik Yak to get the word out about snow days and iced roads,” says Droll, who also points out that Florida State used Yik Yak to alert students of a recent shooting situation.

But don’t expect Yik Yak to stay in school forever. Though Huffington and Droll declined to provide details, they said they plan to take it off campus in the future.

“We’ve seen it work really well at airports and Disney World and just anywhere in the world there’s a collection of people,” says Droll. “Right now we’re focused on colleges and starting there much like Facebook did.”

So, mom and dad, when the time comes, please yak responsibly.

TIME Smartphones

You Asked: How Can I Save My Phone’s Battery When it’s Cold Out?

winter, phone
Getty Images

Wintertime can be a big drain on your phone's battery

If you’ve ever had a hunch your phone’s charge doesn’t last as long in the wintertime, you’re not crazy: Cold temperatures have a nasty effect on batteries.

The scientific explanation for this lies in how batteries work. Basically, their job is to store chemical energy until you need them to power or charge your device. Then they go about converting that chemical energy into electrical energy. However, cold weather causes internal resistance, slowing down the conversion process and resulting in less overall capacity. The kinds of batteries used in most phones are particularly vulnerable to this effect.

Translation? Just like wintertime makes it harder to get your car to start, your phone won’t last as long in cold weather. However, all is not lost — there are some ways to keep your phone as warm and happy as a skier sipping hot cocoa after a day on the slopes.

First, keep your phone as close to your body as you can. Take it out of your backpack or purse and stick it in your jeans or, better yet, in the inside pocket of an insulated base layer. That’ll help your body heat keep things warm. Second, consider picking up an insulated case. These can be a little on the bulky side, but it’s better to have a cumbersome case than a dead phone.

And finally, avoid taking your phone out in really frigid temperatures — the ambient air will suck out your phone’s heat quicker than you can send a text to Mom.

TIME Research

You Asked: Why Am I Cold All the Time?

Illustration by Peter Oumanski for TIME

The science behind your shivering

Frigid weather isn’t solely to blame for your chill.

Of course, frosty outdoor temperatures aren’t warming you up, either. Even if you’re layered in cozy sweaters and toasty corduroys, your hands and feet play an outsize role in determining how warm or cool you feel, explains Dr. Mike Tipton, a professor of human physiology at Portsmouth University in the UK.

Tipton studies the human body’s response to extreme environments—like being dunked in icy water. He says the temperature of your hands and feet dominate your overall sensation of thermal comfort. “You can be warm, but if your hands and feet are cold, you will feel cold,” Tipton says.

This is problematic for many women, who tend to have colder hands than men. A much-cited University of Utah study found that while the average woman’s core body temperature is a smidge above the average man’s, her hands are nearly three degrees cooler.

Tipton says the hormone estrogen contributes to the cold sensitivity many women experience. Estrogen triggers the mechanism that shuts down blood flow to your extremities, he explains. For this reason, research has shown women tend to feel colder during the parts of their menstrual cycle when their estrogen levels spike.

Your metabolism and vascular function also play major parts when it comes to your internal thermostat. “Metabolism is a more complicated concept than it’s often portrayed,” says Dr. Anne Cappola, an endocrinologist at the University of Pennsylvania’s Perelman School of Medicine. But in oversimplified terms, those with a high metabolism burn more calories and enjoy increased blood flow, both of which help heat you up, Cappola says.

“The more muscle mass you have, the higher your metabolism tends to be,” she explains. That’s another lucky break for guys, whose physiological makeup naturally endows them with more metabolism-boosting muscle—although women can counter that biological inequity with diet and exercise.

Cappola says your thyroid also plays an important role in your metabolism and heat production. While the condition is not common, an underactive thyroid—also known as hypothyroidism—is more prevalent in women than in men, and can lead to the kind of drop in metabolic activity that would explain your constant sensation of coldness.

There are many, many more explanations for why you may feel cold all the time, and nearly all of them have to do with poor blood circulation. Anything that messes with your vascular function—from diabetes to old age—will slow the amount of blood passing through your extremities, which in turn could cause you to feel cold, says Dr. Erika Schwartz, who’s written extensively about hormones and their role in how your feel.

So what can you do if you’ve caught a perpetual chill? Start by moving more, Schwartz advises. Movement increases blood flow, which will warm you up. “Sitting at a desk for hours at a time would make anyone feel cold,” she says.

A healthy diet and lifestyle are also essential to proper vascular function. Smoking, poor fitness, or anything else linked to bad blood flow could leave you hugging your shoulders and reaching for space heaters, Schwartz adds. She says a doctor can check your blood for signs of thyroid issues or any other health concerns that might explain your frequent shivering.

You could also embrace the cold. Tipton’s work has shown people have a built-in ability to acclimatize to cold temperatures, which is why you may feel colder in late fall and early winter than toward the end of the snowy season. (This also explains why you can comfortably bust out shorts and a T-shirt on that first 65-degree spring day, while the same thermostat reading would send you hunting for jeans and a sweater in late summer.)

If all else fails, Tipton says, just remember: warm gloves and thick socks are your friends.

Read next: You Asked: Is Sleeping In a Cold Room Better For You?

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TIME Gadgets

You Asked: How Do Virtual Reality Headsets Work?

Virtual Reality
Robyn Beck—AFP/Getty Images An attendee wears an Oculus Rift HD virtual reality head-mounted display at he plays EVE: Valkyrie, a multiplayer virtual reality dogfighting shooter game, at the Intel booth at the 2014 International CES, January 9, 2014 in Las Vegas, Nevada.

If it was a simple as strapping a video screen to your face, we’d all have iPhone visors

Microsoft surprised the world Wednesday with a futuristic headset that will beam 3D images right into users’ retinas. This eye-popping technology certainly looks like it’s on the cutting edge, but actually, the biggest part of it — virtual reality — has been around for years. No, I’m not talking about 1995’s Nintendo Virtual Boy, I’m talking about the underlying science of virtual reality, originally started at NASA 25 years ago.

In essence, virtual reality is taking what people expect to see in the real world as they turn left and right or move forwards and backwards, and replacing it with imagery that moves and behaves the same way, says Mark Bolas, associate director of the Institute of Creative Technologies at the University of Southern California.

“Your perceptual system doesn’t really have anything to tell it that it’s not in the virtual world, so it believes it, and you feel as if you’re present, Bolas says. But he isn’t just a mouthpiece for the head-mounted technology — his department at USC is a major reason why we’re seeing a boom in virtual reality today. His team once included Scott Fisher, who directed NASA’s early virtual reality efforts, and Palmer Lucky, founder of Oculus VR, a leading maker of virtual reality headsets.

To start, think of virtual reality as a stereo video instead of a 3D movie, says Bolas. “When you’re in the theater [for a 3D movie], you see a 3D picture, and you briefly feel presence,” he says. “But if you turn your head left and right, you’re going to see the edges of the screen, so presence is going to be broken.”

On the other hand, virtual reality uses computer graphics, algorithms, and lenses to hide that edge and recalculate the picture as you move. If you turn your head left or right, it will seem like there’s no end to the screen, like it surrounds you in 360 degrees. “All of a sudden, the trick’s complete and you feel like you’re in the space,” says Bolas.

Of course, a 360-degree screen would be prohibitively expensive to make. But Bolas’s lab at USC made a breakthrough in 2011 that helped make virtual reality more realistic, both economically and visually. “We found a magic number for field of view that really gave you this illusion of presence,” says Bolas.

Previous consumer virtual reality displays had fields of view around 40 to 60 degrees, says Bolas. “It’s almost like looking through a toilet paper tube.” By working with an expensive 150-degree screen, USC studied how narrow they could make the field before the feeling of presence was compromised.

“We don’t think about our peripheral vision very much, but it influences us quite a bit,” he says. “It’s wired deep in our brain as a survival mechanism so that if a lion jumps out at you and you see it in your periphery, you react before it ever even gets to the center of your field of view.” The sweet spot for where people catch the lion (or does it catch us?) is around 90 to 100 degrees.

With that figure in mind, USC produced an open source kit that has helped virtual reality developers make more convincing products. And since that time, the technology has taken off, with startups like Oculus getting acquired by Facebook in a $2 billion deal, companies like Sony and Samsung making their own gear, and of course, yesterday’s futuristic announcement from Microsoft.

But the funny thing is, you don’t necessarily need to wait for any of their inventions to try out virtual reality for yourself. In 2012, USC released FOV2GO, a free template for constructing your own virtual reality eyepiece using cardboard and an iPhone 4/4S for a screen. Then, in 2013 they followed up with another free template called VR2GO, which uses the larger-screened iPhone 5 and Android handsets as displays. And the newer model is a 3D-printing file, thank goodness, because mounting a smartphone to your face with cardboard looks awful strange.

TIME Diet/Nutrition

You Asked: Is It Bad to Eat the Same Thing Every Day?

Illustration by Peter Oumanski for TIME

You can get away with eating the same things on loop. But you have to be shrewd about the foods on your grocery list

Meal planning and prep is a pain—especially during the workweek. So it’s easy to fall into the habit of buying, making and eating the same foods day in and day out. Fortunately, that’s not necessarily bad news for your health.

For one thing, “More food variety universally leads to more food intake,” says Dr. Susan Roberts, director of the Energy Metabolism Laboratory at Tufts University.

Imagine a buffet of vegetable dishes versus one large bowl of salad. You’ll eat more from the buffet every time, Roberts says, since we’re “hard wired” for food variety. Unfortunately, that instinct kicks in even if you replace the healthy veggie buffet with its more realistic equivalent: junk food. For that reason, Roberts says trimming your mealtime array of food options is one way to control overeating.

MORE 5 Healthy Eating Habits to Adopt This Year

We have that hard-wired instinct toward food diversity for a good reason. “No one food has all the nutrients we need in the optimum amounts, so eating a variety of foods means you are much more likely to get enough of each one,” Roberts explains.

But how much variety is enough, and how much is too much? A study from Brigham and Women’s Hospital and the Harvard School of Public Health found women who regularly ate 16 or 17 items from a healthy list of foods—which included fruits, vegetables, whole grains, cereals like quinoa, fish, and low-fat dairy—enjoyed a 42-percent drop in death from any cause compared to women who ate fewer than nine of the foods on that list.

On the other hand, there’s some very preliminary research that suggests eating a varied diet may have some not-so-hot health effects when it comes to your microbiome. That’s the network of microorganisms that lives in your body and supports your digestive system, helps control your appetite and performs dozens of other essential functions.

MORE 7 Things You Should Know About Shrimp

Typically, microbe diversity is a good thing when it comes to your gut. But, according to Dr. Daniel Bolnick, an ecologist at the University of Texas, “We’ve shown that in some animals, mixing foods actually reduces the number and variety of gut microbes.”

Bolnick says the takeaway at this stage isn’t that eating a wide variety of foods is bad, but rather that combinations of foods can do unexpected things. “If you know the effect of Food A and the effect of Food B, you can’t predict what will happen to the microbiome when you eat both,” he says. “There’s no question that, as a species, we eat a greater variety of things now then we used to. But whether that’s good or bad for us is still in question.”

So is it good or bad to eat the same stuff every day? If you’re thinking a bagel for breakfast, sandwich for lunch, and meat with potatoes and a salad for dinner, you’re surely going to be deficient in a number of the necessary nutrients your body needs to thrive, Roberts says.

But if you’re packing plenty of healthful, micronutrient-dense vegetables into your simple meal plan—at least six, Roberts advises—you probably don’t have much to worry about. Just be sure the vegetables you eat come in lots of colors, which tend to correlate with different nutrients. And stay away from starchy vegetables like potatoes, which don’t offer a lot of nutrient bang for your buck, she adds.

MORE How You Can Eat More of These 5 Winter Fruits and Veggies

Roberts says the following sample menu would offer pretty much everything your body needs even if you ate it every day: Greek yogurt with fresh fruit for breakfast, a spinach or kale salad with chicken and vegetables for lunch, a fruit-and-nut smoothie for a snack, and some kind of vegetable-and-brown-rice stir fry for dinner.

Of course, there are a thousand other ways you could structure your meals to get all the good stuff your body needs from just a few dishes. And you don’t have to restrict yourself to such a limited plan. The big takeaway here is you also don’t have to go crazy trying to fit a million exotic “superfoods” into your diet if you want to be healthy, Roberts says.

Consider this permission to be monogamous when it comes to your favorite healthy meals.

Read next: You Asked: What’s the Healthiest Sweetener?

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TIME Gadgets

You Asked: How Does 3-D Printing Work?

3D Printing
AFP—AFP/Getty Images A bust of Star Wars film character Yoda is seen printed on a portable 3D printer during the Pravega 2014 science and technology festival at the Indian Institute of Science (IISc) in Bangalore on January 31, 2014.

It’s sort of like an inkjet or laser printer, minus the paper jams, of course.

It’s not every day that 3-D printing will make people’s mouths water. But that was the case at the 2015 International CES, when XYZPrinting unveiled a device that can output icing and dough-based goodies like cookies.

This sweet development is the latest in a long, gradual history of innovation for 3-D printing, which goes back to 1983, when engineer-turned-entrepreneur Chuck Hull invented it in his spare time. Back then, Hull’s day job was curing rugged coatings onto tables using UV lights. But he postulated that focussing that light like a laser would allow the liquid resin with which he was working to form shapes. That was the basis for stereolithography (SLA), the advent of 3-D printing, and eventually the basis for his company, 3D Systems.

Today, 3-D printing essentially lets computer users take digital files and turn them into physical projects. If that sounds like paper or 2-D printing, that’s because they’re very similar. In 2-D printing, a file is created and sent to a printer, and a page is output. 3-D printing’s workflow almost exactly the same: a file is created and submitted to a device, the product is output, and it may require some finishing touches when done.

SLA is the earliest form of 3-D printing, and it’s very high quality. Originally used for what product developers call rapid prototyping, SLA was designed to give designers the ability to touch, feel, and compare the goods they were making. A slow-moving technology, it can take hours or days to print using SLA machines, which shines a laser into a pool of liquid, building the form layer-by-layer as a base support gradually moves the shape that’s being made. Despite this painstaking process, SLA’s quality is so good that you might never know your object was 3-D printed. SLA is used primarily only in commercial printing.

Another kind of 3-D printing is Selective Laser Sintering (SLS). “Selective Laser Sintering is a powder and laser type technology, but boy doesn’t that sound similar to toner and laser technology that’s used in a photocopy?” says John Hauer, founder of 3DLT, a company that prints 3-D products for retailers. And in essence SLS is very similar to a laser printer, only instead of scoring the toner onto a piece of paper, this three-dimensional technology shines its laser onto a bed of powder, turning it into hardened material. Also primarily a commercial technology, SLS can be used in many ways, allowing people to produce products in everything from nylon-based plastics to metals, including stainless steel, silver, gold, and titanium.

The third major kind of 3-D printing, Fuse Deposition Modeling (FDM), is the one that’s making the most waves with consumers right now. “That is what people envision as kind of like weed whacker string, where a plastic is inserted into a hot end and then melted, layer by layer, to achieve the product,” says Hauer. And to continue the paper printing analogy, FDM is also very similar to inkjet printing, where ink is extruded through a print head onto a page.

While this technology is getting better all the time, it still, literally, has some rough edges. But Hauer says some people like that. “You can feel the ridges—you can scrape your thumb along it and it’ll actually make a sound,” he says. “Because people are so interested in 3-D printing, the ability to touch and feel a 3-D printed product and tactilely know it’s different than a mass produced product has actually been advantageous. It’s helped them better understand the technology.”

And of course, food is something that everyone understands, which is why the edible printing technology made such big headlines at CES. Our future holds chocolate flowers, elaborate cake toppers, crazy confectionaries and other exciting edibles, says Hauer. “It has the opportunity to be a big thing,” he says. “We’ve even seen 3-D printed cheese, 3-D printed peanut butter and some of those things.”

But the real question is, will 3-D printed doughnuts taste as good as the real thing?

TIME Aging

You Asked: Can Smiling A Lot Really Cause Wrinkles?

Illustration by Peter Oumanski for TIME

The answer will make you frown (another expression that creates age lines)

Whether you’re talking, scowling or smiling, a groove forms on your skin the moment you move one of your facial muscles. That groove is perpendicular to the movement of the underlying muscle, explains Dr. Anthony Rossi, a dermatologist at Memorial Sloan Kettering Cancer Center. “For example, forehead grooves are horizontal because our forehead muscle pulls up,” Rossi says.

When it comes to your smile, the largest of the lines that form are the “nasolabial folds”—those big parentheses of skin that arc downward from the sides of your nose to the corners of your mouth, explains Dr. Marc Glashofer, a New York-based dermatologist. Those folds appear every time you smile. And as you grow older, those happy-face grooves don’t fade away once you stop beaming, Glashofer says.

But don’t blame your smile. The real culprit is your skin’s diminishing elasticity.

Rossi calls the biological changes that hurt your skin’s rebound abilities “intrinsic aging.” These include breakdowns to the underlying structure of your skin due to factors like fat loss and muscle atrophy. Rossi says your genetic makeup also affects how your hide holds up to years of smiling. “We know different ethnicities age differently,” he says, adding that your skin’s natural melanin concentrations and oil production also play a role in how quickly your smile groves will start to leave their mark. Unfortunately, many of those variables are out of your hands.

But here’s one factor you can control: ultraviolet radiation exposure from sunlight. “This is actually the number-one cause of winkles,” Glashofer says. The more sun your skin soaks up, the more its connective tissue breaks down, leaving it less firm and less elastic.

For that reason, Glashofer and Rossi recommend the daily use of a sunscreen that guards against both UVA and UVB rays. Both dermatologists also advise keeping your skin well hydrated, which starts with drinking plenty of water. Rossi says H2O is a major component of your dermis—the layer of skin that houses many of the structural proteins that keep you looking youthful. He also suggests using a skin moisturizer, which helps your skin lock in water.

Retinol-based creams are also aces at fending off age lines, Rossi says. “They not only promote the formation of new skin cells, but they also increase collagen production, which improves the appearance of wrinkles and slows their formation,” he explains.

Of course, you could also try to limit your smiles. But you’d be forgoing the immune system-boosting, stress-lowering benefits of a good laugh. “I would never tell anyone to avoid smiling,” Glashofer says. “You are truly blessed to have an abundance of smiles in your life.”

Read next: You Asked: Does Laughing Have Real Health Benefits?

TIME Diet/Nutrition

You Asked: What’s the Healthiest Sweetener?

Illustration by Peter Oumanski for TIME

Why sweet and good-for-you might not go together

You’ve heard sugar is bad news. But what about all those low-cal or no-cal substitutes? And organic honey! That has to be healthier, right?

“Honey, table sugar—doesn’t matter. It’s all sucrose, and your body metabolizes it the same way,” says Dr. Robert Lustig, a pediatric endocrinologist at the University of California, San Francisco. Lustig is also board president of the Institute for Responsible Nutrition, and presenter of “Sugar: The Bitter Truth”—a much talked about YouTube lecture that lays out the perils of the sweet stuff.

Apart from its high calorie content, which contributes to weight gain and obesity, sugar messes with your body’s insulin responses, Lustig says. Heart disease, diabetes and fatty liver disease have all been linked to the types of insulin issues sugar provokes.

“Sugar also binds to proteins in your body and causes damage,” he says—the same kind that browns fruit left out on your kitchen countertop. “We’re all browning. That’s part of aging,” Lustig explains. “But sugar causes you to brown seven times faster.”

There’s more to say on the subject of sugar and your health, but the bottom line is that too much sugar is bad for you, and most Americans consume way more than they should. “Your liver can process roughly six to nine teaspoons a day without significant issue,” Lustig says. “The average American consumes 19.5 teaspoons a day.” And while honey may contain antioxidants or compounds that, on their own, may offer some benefits, “The sucrose in honey is still sucrose,” Lustig adds.

Unfortunately, when it comes to artificial sweeteners and other sugar alternatives—from stevia to sucralose—the health picture grows foggier, not clearer. “Some people believe that, because some artificial sweeteners have no calories, they have no consequences,” says Dr. Yanina Pepino, research assistant professor in medicine at Washington University in St. Louis. “But we know that’s not true.”

Pepino’s research has demonstrated that sweet tastes—even those produced by non-caloric sweeteners—have the power to ramp up your body’s insulin responses. She says there’s also data suggesting non-caloric sweeteners contribute to the development of metabolic disorders and type 2 diabetes.

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More new research has hinted that artificial sweeteners may mess with your gut’s microbes, the tiny organisms that live in your digestive system and help manage the ways your body breaks down and processes the stuff you eat. Like opening Pandora’s box, Pepino says any changes to the gut’s microbiota may lead to widespread negative health consequences.

“When it comes to sugar substitutes, we just don’t know enough,” she says—a sentiment Lustig repeats over and over again. And not knowing makes choosing between sugar and sugar alternatives a thorny proposition.

While some new sweeteners may claim to be healthier than others, the fact is they’re simply newer, so there’s not as much known about them, Lustig says.

In the end, both he and Pepino agree there’s only one right answer if you’re watching out for your health: Limit the amount of sweet stuff in your diet.

“I know people won’t like that answer, but that’s the only one I can give,” Pepino says. “There’s just no way to say one is better than another without a lot more data.”

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