Sleeping Beauty was onto something. Turns out, your ticket to healthier, younger-looking skin may lie between the sheets rather than on the shelf of your medicine cabinet.

While you’re fast asleep, your body is hard at work, making repairs like construction workers on the nightshift. For example, when you’re in deep sleep, human growth hormone production increases. Your normal release of this hormone plays a key role in healing cells and tissues throughout your body, including your skin.

Not getting enough sleep (and according the Centers for Disease Control and Prevention, an estimated 50-70 million U.S. adults have a sleep or wakefulness disorder) cuts that crucial repair time short, which can wreak havoc on your skin. Fine lines become more prominent, dark circles crop up and your complexion turns pale, dull and droopy.

Getting enough Vitamin Z makes you appear more attractive—sort of a reverse beer-goggles effect. In one study, people rated photographs based on attractiveness and whether the individuals in the photos looked healthy or unhealthy as well as tired or not tired. The faces of sleep-deprived participants were ranked as less healthy, less attractive and more tired compared to when they were well rested.

So how exactly does being robbed of your rest affect your appearance? “Several theories exist,” explains John Axelsson, an associate professor at the department of clinical neuroscience at the Karolinska Institutet in Stockholm, Sweden, who co-authored the study on sleep and appearance. “Sleep may actually affect the skin by reducing its capacity to recover properly, or sleep deprivation may affect muscle tone, resulting in a slightly less attractive appearance.”

THE STUDY, EXPLAINED: Sleep Boosts Beauty

When you sacrifice slumber, you decrease the ability of the skin barrier—also known as the stratum corneum, or the outer-most layer of skin—to recover from the daily damage it endures. That’s problematic because the stratum corneum plays two important roles when it comes to healthy-looking skin: It locks in moisture and prevents foreign microorganisms from getting in. Cells that make up the stratum corneum contain keratin, which is a protein that keeps skin hydrated by preventing water from evaporating.

Not getting enough sleep affects the skin barrier’s ability to do its job and can lead to dehydration, which, in turn, makes fine lines more noticeable. “Moisture helps plumps up your skin—it blows out your wrinkles,” says Robin Ashinoff, M.D., director of cosmetic dermatology at Hackensack University Medical Center in New Jersey. “Your skin droops more because you don’t have that plumpness. You’ve deflated the balloon.” 

Dehydration can also trigger the classic signs of sleep deprivation—dark circles. That’s because there’s less fluid to obscure the blue blood vessels that reside just under your eyes. These blood vessels become more noticeable on the surface, showing up as dark, under-eye circles. “Overall you also look paler because the blood vessels in your face aren’t as full,” says Dr. Ashinoff. In addition to all that, “When you sleep, it’s a regenerative time, so if the skin doesn’t have a chance to turn over, you have dead skill cells sitting on top, causing the skin to look dull.”

MORE: How Much Sleep Do You Really Need?

A weakened skin barrier can leave you more vulnerable to foreign microorganisms. Think of the stratum corneum as a bouncer to an exclusive nightclub, carefully picking and choosing who gets to come in. Insufficient time in the sack makes him less discriminating about who enters the club, which is why a compromised skin barrier is associated with inflammatory skin conditions, such as atopic dermatitis, eczema and psoriasis.

Your immune system also becomes compromised when you miss out on getting enough rest. But that doesn’t just leave you more vulnerable to sickness. These changes in the immune response may affect collagen production as well. And collagen helps you maintain a youthful appearance by acting as scaffolding—holding up your skin so it doesn’t wrinkle and sag. Add to that the fact that when you’re tired, your muscles, including facial ones, are more likely to tense up, which can exacerbate your current wrinkles and bring on more fine lines and wrinkles over time.

What’s more, not getting enough z’s may bring on breakouts. “Lack of sleep correlates to physiological stress,” explains dermatologist Neal Schultz, M.D., co-author of “It’s Not Just About Wrinkles: A Park Avenue Dermatologist’s Program for Beautiful Skin—in Just Four Minutes a Day.” Levels of cortisol—the stress hormone that breaks down skin cells and is linked to acne—also spike when you’re missing out on some much-needed pillow time.

BEAUTY AHA: Sleep Eight Hours to Stay Healthy and Happy

Speaking of pillows, your sleeping position can also put a crimp in your complexion. “If you sleep on your side or front, rather than your back, it’s like you’re folding over your skin—except it’s sustained pressure,” says Dr. Schultz. “It’s breaking the collagen, which can give you wrinkles and make your skin look saggy.” Sleeping on your back helps prevent fine lines from being etched into your skin overnight. But if you can’t sleep prone, try slipping on silk or satin pillowcases instead, which are more forgiving and won’t tug at your skin, causing fine lines.

The bottom-line: “Sleep is the body’s natural beauty treatment,” says Axelsson. Rather than shelling out cash on expensive creams or relying heavily on concealer and coffee, try pulling a Sleeping Beauty and getting a full night’s rest instead.