We all have our daily habits, from the number of times we hit the snooze button to whether we shower in the morning or at night. We’re not here to tell you how to live your life, but there is some surprising science behind the time of day it’s best to suds up and get squeaky clean. Check it out and then choose the time that works for you—or shower twice, because dang it if we can’t have it all.

Morning Glory

If you’ve got a tough week ahead at work and really want to perform at your creative best, showering in the morning is the way to go, says Shelley Carson, Ph.D., a psychology lecturer at Harvard University. The logic traces back to something psychologists call the incubation period—the time between posing a problem and having that “aha” moment.

“If you were to come up with a problem that you wanted to solve creatively, and you were working and working on it and couldn’t come up with a solution, then you could put it on the back burner of your mind and allow it to stew there while unconscious processes mull it over,” Carson says.

These processes work best in the shower because it’s a place where you enter into a relaxed but still alert alpha brain wave state, Carson explains. That’s the same kind of state you enter while meditating or after aerobic activity. When you’re in alpha (as opposed to beta, the state where you’re really focusing on a question), your cognitive processes relax, renew, and regenerate—letting the top-notch ideas effortlessly bubble to the surface.

And like a slow cooker meal at the end of the day, those ideas are often just what you’ve been waiting for. Write down your eurekas when they hit—yes, someone actually invented waterproof notepads—and come into work firing on all cylinders.

Showering in the morning has one other benefit for self-accepting zombies who get a little clumsy with the razor: Our bodies have a surge of clot-forming platelets from 6 a.m. to noon, which means that if you knick yourself, the bleeding should stop soon.Concurrent morning increase in platelet aggregability and the risk of myocardial infarction and sudden cardiac death. Tofler GH, Brezinski D, Schafer AI. The New England journal of medicine, 1987, Jun.;316(24):0028-4793. Mechanisms underlying the morning increase in platelet aggregation: a flow cytometry study. Andrews NP, Gralnick HR, Merryman P. Journal of the American College of Cardiology, 1997, Jan.;28(7):0735-1097.

Suds Yourself Sleepy

On the other hand, if you always find yourself awake and full of energy past your bedtime, a nighttime shower is the way to go, says Christopher Winter, M.D., a fellow at the American Academy of Sleep Medicine and medical director at the sleep center at Martha Jefferson Hospital.

It all has to do with your body temperature, which rises with the warm water and then drops once you dry off. “That rapid cooling after you get out of the shower or out of the bath tends to be a natural sleep inducer,” Winter says. “So it’s a nice way to fool your body into thinking it’s time to go to bed.”

Plus relaxing showers tend to reduce cortisol levels (good-bye stress), which makes is easier to catch some zzzs, Winter says.

Even if you sleep like a baby, you might want to opt for night showers to keep your skin clean, says Bethanee Schlosser, M.D., Ph.D, an assistant professor of dermatology and director of the Women’s Skin Health Program for Northwestern Medicine. We’re not just talking about on days you sweat it out. The dirt and oil that come from environmental pollutants (like the lovely grime you come in contact with on the subway) can clog your pores if you don’t shower before hitting the hay.

And since your face’s oil production hits its peak around 1 p.m., you could be more prone to acne flare-ups if you don’t wash off before bed, Schlosser says. Oil production is usually minimal in the middle of the night unless you’re a sweaty sleeper—in which case, wash the sweat off your face in the morning and start fresh.

The Takeaway

If you’ve got a brain-buster on your hands, morning showers are the perfect time to work it out, assuming you can space out long enough to let incubation happen. Have trouble with acne or in search of an elusive snooze? Let the warm water wash away irritating oils (with the help of a little soap), melt away your cortisol, and ready you for a restful night’s sleep.

But of course, things aren’t always so cut and dry (or damp, if you catch our drift). Showers at any time can induce that defocused incubation state, Carson says, so night showers (or even midday ones, if your office is truly New Age) can also draw out your best ideas. Don’t have time for a shower on your lunch break to get those ideas flowing? Take a walk instead.