It takes one cruddy night of sleep for someone to remark on how terrible you look. Like, Gee, thanks, as if you didn’t already feel like a shell of yourself, now you get a reminder that you’re radiating exhaustion. And if you stack a few nights of sleep deprivation on top of each other, you go from looking like a young Johnny Depp to a Johnny Depp right now.

And that's just a few nights. Imagine what years of poor sleeping can do to your appearance, even if you’re hibernating on weekends to play catch up. It takes a toll on your eyes, your complexion, your hair. You might not realize it, but you’re falling victim to stress. I spoke with a real live doctor—Dr. Michael Swann, MD—to figure out what exactly are the worst ways that sleep deprivation affects your appearance.

Swann spoke with me about how being poorly rested not only has short term, next-day effects, but also long-term consequences. Here’s what he had to say about the importance of sleep on your appearance, and how to remedy the side effects (both immediate and long term) of under-sleeping.

How is sleep directly related to the health and healing abilities of the skin?

Swann: “Although the specific effects of sleep in skin and hair health have not been entirely illuminated, we do know that quality sleepers can heal from skin problems more rapidly. Poor sleep habits also lead to stress, as evidenced by increased cortisol levels in the body. Cortisol is known to be associated with poor wound healing, but there are likely multiple factors at play.”

Related: How Stress Affects Your Appearance

How many hours should an adult male get every night?

Swann: “Generally a man requires 7-8 hours of sleep per night, but this can vary from 5-10 hours. It is important to listen to your body and maintain a consistent sleep habit. “

Why is it important to use products overnight, especially if one isn’t getting these 7-8 hours of sleep?

Swann: “Overnight skincare becomes more important for men as they age. Products and protectants can help your body to stay more hydrated and promote more even turnover, which is associated with less wrinkled and younger looking skin. Much like exercise, skin regimens are not very effective unless they are adopted as a daily or nightly habit, and most skin regimens take 3-4 months in order to see best results. For men looking for a quicker fix, we often combine a good at-home regimen with in-office procedures.” (So, if you want results faster, visit your dermatologist to figure out the best regimen for you.)

Why do our eyes get puffy and dark when we don't sleep?

Swann: “There is a clear association with puffy eyes after a poor night of sleep, but the exact mechanisms are unclear. When you stay up and don't sleep, your eyes tend to be dry and irritated, which leads to inflammation and swelling or puffiness in the eyes. This can make your eyes look older and your eyelids show more fine lines. Tired eyes are also prone to twitching due to muscle fatigue.”

What types of products can remedy tired, puffy eyes?

Swann: “Ocular lubricants before bed can help moisturize tired eyes and minimize irritation. Hydrating eyelid products with hyaluronic acid (like Mario Badesco’s) minimize dark circles well. Mineral-based sunscreen (like Badger’s with zinc oxide) can often do a nice job minimizing the discolorations associated with tired eyes.”

Related: The Best Eye Creams for Looking Human Again After a Long Night of Partying

What is your favorite product to keep skin looking firm and alert?

Swann: “I really like Skin Medica's HA5 to hide imperfections and really maximize moisture in the outer skin layers. It contains hyaluronic acid, which holds on to water molecules as well as dimethicone which helps it to spread really evenly.”

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What are the long-term effects of routinely under-sleeping?

Swann: “It is really difficult to know the specific realities of someone who has a chronic lack of sleep over many years, and understand which factors are preeminent. Aging is a multifactorial process and is heavily influenced by genetics, UV radiation exposure, and stress. Routine under-sleeping can cause permanent damage to the skin and eyes after an initial period of reversible damage. How quickly sleepless nights will add up to ‘big changes’ in your skin is heavily dependent on genetics and the individual, but we can see hair loss and skin changes quickly from increased stress which is commonly associated with sleep deprivation. Whether the stress or the poor sleep is the primary driving force is difficult to reconcile, because they tend to be paired.”