TIME Diet/Nutrition

You Asked: Why Can’t I Eat Raw Meat?

Illustration by Peter Oumanski for TIME

Well, you could. But you’d be rolling the dice.

Sushi restaurants are nearly as rampant as Starbucks stores. So why is raw fish okay to consume, while raw beef, pork and other land animals are typically not on the menu?

For one thing, the parasites and bacteria that set up shop in raw animal meat are different and more dangerous than the ones you’d find in raw fish, says Dr. Robert Tauxe, deputy director of the Division of Foodborne, Waterborne and Environmental Diseases within the Centers for Disease Control and Prevention (CDC).

From salmonella and parasitic E. coli to worms, flukes, and the virus hepatitis E, Tauxe says the creepy crawlies that may inhabit raw meat tend to be more harmful to humans than the microorganisms you’d find in raw fish. “Perhaps it’s because our bodies are more closely related to land animals than to those of fish,” he explains.

The way animals are slaughtered and packaged also has a lot to do with their health risks, says Dr. Eugene Muller, a microbiologist at Framingham State University in Massachusetts. “Parasites and bacteria tend to come from an animal’s gut, not its muscle,” he says. If your butcher nicks open an animal’s intestines, any harmful microorganisms released could contaminate all the meat the butcher is preparing.

Packaged ground beef is particularly likely to house sickness-causing bacteria or parasites, says Dr. Lee-Ann Jaykus, professor of food science at North Carolina State University. That’s because a single package of ground beef could contain meat from dozens of cows, Jaykus says. “One contaminated animal could corrupt dozens of batches,” she explains. For that reason, she advises never eating hamburger that’s red or rare in the center.

Both Muller and Jaykus say whole cuts of beef are less risky because they come from a single animal. “Anything harmful lives on the surface of the meat, not inside the muscle,” Muller says. “So if you like your steak very rare, just searing the outside will likely kill anything harmful.”

Jaykus agrees, but says you have to watch out for something called “mechanically tenderized meat,” which involves puncturing the beef with small needles or blades to make it more tender. She says many restaurants and grocery stores sell meat that’s undergone this process because it improves the texture of cheaper cuts like sirloin or round. “This process can force contaminants into the muscle tissue where searing the outside won’t kill them,” she says. “You don’t see this at high-end steakhouses, but it’s an issue with steaks purchased for home cooking and in some restaurants.”

Most of these concerns and caveats also apply to lamb, pigs, chickens and other land animals—though Muller says pigs and chickens tend to carry some harmful microorganisms you don’t find in cows or sheep. “But I don’t think many people really want to consume raw pig or raw chicken,” he adds.

Fish is a different story. Setting aside the differences between fish and mammals when it comes to the number, type, and frequency of potentially dangerous organisms they may harbor, fish tends not to be ground or mixed. That lowers the likelihood of a single disease-carrying salmon or tuna contaminating others, Jaykus says.

Also, any raw fish you consume at a sushi restaurant are caught in colder waters and frozen before you eat them. “This kills the encysted worms and other parasites,” Tauxe says. Unfortunately, freezing doesn’t kill parasitic E. coli and many of the harmful microorganisms you’d find in meat, Muller says.

With raw fish, oysters and other uncooked seafood, you’re taking a risk, Muller says—though not nearly as big a risk as eating that bloody tenderloin or tartare.

Read next: The 50 Healthiest Foods of All Time (With Recipes)

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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 Diet/Nutrition

You Asked: Should I Take Probiotics?

Illustration by Peter Oumanski for TIME

From strengthening your brain to slimming your belly, you’ve likely heard the promises of probiotics. Headlines call them the future of preventive medicine and disease treatment. But for now, the key word is future.

“For those with bowel disorders or urinary tract infections, there’s little doubt probiotics can be helpful,” says Dr. Shekhar Challa, a gastroenterologist and author of Probiotics For Dummies. But for healthy adults? “Things are still open to interpretation,” Challa says.

Here’s what scientists know now: Your body houses hundreds of trillions of bacteria, many of which reside in your gastrointestinal tract. Of those gut bacteria, 90 percent appear to be system-supporting or “friendly,” Challa explains. Those are the probiotics. And the more types or “strains” of probiotic bacteria you have in your gut, the better.

Plenty of evidence shows that a diverse population of gut bacteria aids digestion and immune health, Challa says. Two bacteria strains in particular, Lactobacillus and Bifidobacteria, seem to be supportive, he says.

One recent U.K. study found Lactobacillus may combat the type of insulin resistance that contributes to obesity and the development of type 2 diabetes. If the tight junctions between the cells in the lining of your gut break down, the gap allows “inflammation-causing agents” to get into your bloodstream and cause trouble, says the study’s author, Dr. Carl Hulston of Loughborough University. But probiotics appear to seal those junctions and prevent this “leaky gut” situation.

“It’s a little too early to advise probiotic consumption as a prevention or cure for diabetes,” Hulston says. “But our initial findings are very positive.”

Read through the scientific literature on probiotics, and you’ll run into hundreds of similar statements. Probiotic potential seems limitless. The problem is figuring out how to get the right types of bacteria to set up shop in your body.

“You can eat probiotic foods like yogurt or kefir, which I think everyone should consume on a daily basis,” Challa says. “But just because you’re ingesting a probiotic doesn’t mean it’s being incorporated into your gut.” Harsh stomach acids and other aspects of digestion can kill the bacteria before they establish residency, Challa says.

Probiotic supplements—some of which contain coatings or ingredients designed to protect their contents from your belly’s acids—may be more effective, Challa says (though it should be noted that he’s part owner of a company that produces these types of supplements.) But he’s quick to add there are still a lot of roadblocks. Your age, your gut’s current micro-organic makeup, your diet and many other factors make it hard to offer broad recommendations, he explains.

It gets even murkier when you consider research from Dr. Daniel Bolnick and colleagues at the University of Texas. They’ve shown that—at least in some animals—eating a wider variety of foods actually reduces the number of probiotic bacteria in the intestinal tract. “We looked at the effects of diet mixing on gut microbes,” Bolnick says. “And we found the more you mix, the fewer you have.”

This doesn’t mean that consuming many different types of bacteria is bad. It just raises questions, Bolnick says. “Combinations of foods can do unexpected things,” he adds.

So what’s a wannabe bacteria-booster to do? Challa says that eating probiotic foods on a daily basis, like yogurt, kefir and kombucha may be beneficial, and certainly won’t harm you. “There’s no evidence that people can overdose on probiotics,” he says. And for those with gastrointestinal issues, he strongly suggests a probiotic supplement containing Lactobacillus and/or Bifidobacteria. (Just run it by your doctor first.)

When it comes to all the other benefits you’ve heard about, it’s too early for experts to offer firm advice. “There are just too many questions and not enough hard data,” Challa says. “The potential is there. The understanding is not.”

Read next: Is It Bad To Eat the Same Thing Every Day?

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TIME toxins

You Asked: Is Perfume Bad for Me?

you-asked-perfume
Illustration by Peter Oumanski for TIME

Many people suffer an allergic reaction to perfume—even when it's on someone else

For some it’s intoxicating. It may also be toxic.

From sneezing and wheezing to rash and headache, many people suffer an allergic reaction to perfume—even when it’s on someone else. “Anything that gives perfume an odor is very likely going to be an allergen,” says Dr. Heather Patisaul, a biologist at North Carolina State University who studies the way environmental exposures mess with human development. That means your cologne- or perfume-soaked colleague could be the cause of your runny nose.

“Look at your perfume bottle and read the ingredients,” she suggests. “It reads like a chemistry book.” You can get lost among all the benzyls and ethyls. But it’s the ingredient listed simply as “fragrance” or “parfum” that worries public health researchers like Patisaul. “Those terms are a catchall for 10,000 different ingredients,” she says.

Thanks to trade-secret laws protecting perfume and cosmetic makers from divulging the specific formulas for their scents, Patisaul says there’s usually no way to know exactly which of those 10,000 ingredients you’re dabbing onto your neck or wrist. But a good bet is that any scented cosmetic—from perfume and cologne to body lotion and deodorant—will contain a group of petroleum-based chemicals called phthalates.

“Phthalates are wonderful for cosmetics because they make things smear really well,” Patisaul explains. When it comes to perfume, phthalates keep all the liquid’s different elements suspended and evenly distributed, adds Caroline Cox, research director for the non-profit Center for Environmental Health—a watchdog group that monitors chemical-related public health concerns.

So what’s the problem? Some phthalates—namely one called diethyl phthalate (DEP)—are shown to disrupt our hormones, including testosterone. That’s a big concern for pregnant women, Patisaul says. “There’s evidence connecting phthalates to developmental disorders, especially among newborn boys,” she explains.

More research has linked DEP to poor lung function and myriad sperm issues, from lower counts to reduced motility, Cox says. Which means men—particularly adolescents who fumigate their still-developing bodies with aerosolized body sprays—could be at risk. “I mean, you’re purposely spraying these chemicals close to your body and rubbing them right on your skin,” Cox says. “There’s no question people are exposed.”

In women, research has linked phthalate exposure to problems such as polycystic ovarian syndrome, a cluster of symptoms that can include trouble conceiving, irregular periods, and hormonal imbalances that can lead to irregular hair growth and acne. Fetal exposure is better understood, and has some experts concerned.

Read more: Beauty Products May Trigger Early Menopause

What isn’t clear: Just how much phthalate exposure is too much. “It’s not like we can deliberately expose a bunch of pregnant women or boys to phthalates and see what happens,” Patisaul says. “So coming up with hard proof is difficult.” That same dilemma helped cigarette companies dodge health regulators for decades. And it’s bad news for American perfume and cosmetic users. “Our regulatory system assumes a chemical is safe until proven harmful,” Patisaul says. “In a lot of other countries, it works the opposite way. The burden is on the chemical producer.”

As a result, some perfume ingredients banned in Europe are still available in the U.S., Patisaul says. (France, the ne plus ultra of perfume-loving nations, is also one of the most strictly regulated when it comes to cosmetic components.) The list of banned ingredients includes natural animal musks and plant extracts that, for some, are potent allergens.

Read more: This Makeup Additive Is Linked To A Lower IQ

To protect yourself (and your coworkers), you could swap all your fragranced products in favor of unscented cosmetics, Patisaul says. Cox says you can check the safety of some ingredients and products that contain them using resources like Skin Deep, a product safety database run by the non-profit Environmental Working Group.

Pregnant women in particular should consider this sort of medicine-cabinet purge.

If you can’t bear to part with your favorite perfume, at the very least go easy when you apply it. And ditching scented lotions, deodorants, shampoos and aftershaves will still lower your exposure, Patisaul says. “You could argue endlessly about what is or isn’t a safe threshold,” she says. “The truth is, we’re only beginning to understand how these chemicals disrupt the body.”

Spritz at your own risk.

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 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 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 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: Are Cleanses Healthy?

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Beware the detox deception

Skip the lemon water and extravagant juices. Peculiar potions and potables that claim to “detoxify” your body are just the latest reincarnations of snake oil.

“I always look for science to inform my recommendations,” says Dr. Joy Dubost, a dietitian, food scientist and spokesperson for the Academy of Nutrition and Dietetics. “But to date, there’s no solid science backing any of these cleansing or detox approaches for weight loss or health.”

Of course, the word “cleanse” has been applied to a huge range of diets, from those that replace one or two daily meals with fruit smoothies to the more extreme types that advocate drinking little more than spiced water for a week or longer. The extreme kind—those that could never permanently supplant a normal diet—don’t tend to have long-lasting effects.

Not only is the hard science on cleanse diets missing, but Dubost also says the premise underlying these drinks—that you can somehow flush your system of pollutants—doesn’t pass a basic sniff test. “Your body has built-in mechanisms for detoxification, including your liver, kidneys, and gastrointestinal system,” she says. “Swallowing some kind of solution isn’t going to further enable those organs, so the whole premise of detoxifying is inaccurate.”

“I’ve also never seen an explanation for what ‘cleanse’ or ‘detox’ diets are cleansing or detoxifying your body of,” Dubost adds. “I think the vagueness there may be part of the appeal.”

Put another way, if you’re eating a healthy diet packed with fruits, vegetables, whole grains and lean protein—the kind of sustainable diet that will help keep your weight down and lower your risk for many diseases—your body has no use for any radical detoxification measures. And if your diet is poor, pounding juice for a week isn’t going to do you any good.

“You’ll drop some water weight on these cleanses because you won’t be consuming very many calories,” Dubost says. “But that weight will come back when you start eating again.” The kind of severe calorie restriction associated with cleanse diets can also lead to muscle breakdown and feelings of extreme fatigue, as well as headaches, irritability, cramping and diarrhea.

But what about those people who say they just feel amazing after completing a cleanse? Dr. Fabrizio Benedetti, a professor of neurophysiology at University of Turin Medical School in Italy, has written books about the placebo effect. “Feelings, perceptions, and a sense of well-being are very much influenced by placebos,” he says.

Benedetti cites a recent milkshake study from Yale University. During the study, researchers gave people a milkshake and told them it was either a 620-calorie “indulgent” shake or a 140-calorie “sensible” shake. Although all the milkshakes were identical, hunger-producing hormone levels plummeted in the “indulgent” milkshake sippers, but remained elevated among the “sensible” shake group. In other words, mind outweighed milkshake when it came to people’s hunger.

“We see placebo effects in the world of health science all the time,” Dubost says. “The mind is powerful, and I think it plays a big role for people who feel like going to diet extremes will offer them more benefits.”

All that said, Dubost admits she can see one potential benefit to cleanse diets. “Some people like ‘flipping the switch,’ or doing something extreme to kick start a new eating plan,” she says. If you know your diet isn’t great and you want to make a change, doing something a little over the top to initiate a hard break or “reset” from your old ways could put you in the right mindset to stick with a healthier eating routine, she says.

Like using the start of the New Year as motivation to change your life, initiating a cleanse for a few days before adopting a healthier well-rounded diet could have some psychological benefit, Dubost says. But again, that cleanse won’t be doing your health any favors.

“It’s amazing what people put their bodies through for a quick fix,” Dubost says. “If they’d put that kind of energy into a less-restrictive, more-sustainable diet, they’d have a lot more long-term success.”

Read next: You Asked: What’s the Best Way to Whiten My Teeth?

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TIME toxins

You Asked: Are Hot Tubs Dangerous?

Illustration by Peter Oumanski for TIME

You’ve heard the rumors. The reality is probably worse.

Most men know that submerging their nether-parts in hot water can mean bad news for baby-making. And of course, the question of a hot tub’s water-to-urine ratio is a constant concern. But usual suspects aside, some very scary health issues have been linked to hot tub use.

“We call it ‘hot tub lung,’” says Dr. Cecile Rose, an environmental and respiratory health expert at National Jewish Health, a medical center in Denver. Rose is describing a type of lung inflammation that she and other researchers have linked to hot tubs. A specific kind of bacteria found in public water systems—called Nontuberculous mycobacteria—ends up in the mist produced when you switch on a tub’s bubbles.

“When you turn on the jets, this bacteria becomes aerosolized, and you inhale it,” Rose explains. Once it reaches your lungs, the bacteria can cause symptoms like fever andshortness of breath. If you continue to use your tub, the inflammation persists and worsens, and can cause lasting fatigue, weight loss and other more serious side effects. “A lot of doctors don’t ask if a person with these symptoms has been using a hot tub, and people become very sick,” Rose says. “If you keep using your tub, taking antibiotics or steroids won’t do any good.”

Even if you never use the bubble jets, you may still be at risk for so-called hot tub lung. “The jets are a very efficient delivery system, but that doesn’t mean turning them off is safe,” Rose adds. And no, you can’t just crank up your water supply’s chlorine and bromine disinfectant levels. Too much of those can lead to respiratory issues too, Rose adds.

More bad news: Mycobacteria aren’t your only unwelcome bathing buddies. Another type of bacteria called Pseudomonas can cause eye, ear and skin irritations, Rose says. She also mentions a germ called Legionella that can lead to Legionnaire’s disease—a severe form of pneumonia. Like mycobacteria, Legionella gets into your system through mist or steam inhalation, according to the Centers for Disease Control and Prevention (CDC).

“People with compromised immune systems—older adults, those with diabetes or on chemotherapy drugs—are most at risk, and the mortality rates associated with Legionnaire’s are actually quite high,” Rose explains.

That’s not all. A study in the Journal of the American Medical Association found the virus that leads to genital herpes can survive for hours on the plastic seats you’ll find in some hot tubs.

Blame the hot water temperature for most of these health hazards. Just as you enjoy a toasty soak, bacteria and germs thrive in the cozy comforts of warm water, Rose says. A report on Legionella from the CDC says higher water temperatures make it more difficult to maintain the proper disinfectant levels required to kill off the microscopic creepy crawlies that can make you ill.

That doesn’t mean all hot tubs are sickness-spreading cesspools. If you own your own tub, and you’re rigorous about cleaning it frequently, changing the water and checking its disinfectant levels, you can probably breathe easy. (Literally.) But when it comes to public pools, you might be taking a risk every time you slide down into those invitingly frothy bubbles.

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