A night spent tossing and turning, waking up to damp sheets, pajamas that stick to you—all signs you might be a hot sleeper. But why do I sweat when I sleep, you ask? There are a lot of factors that could be at play here, according to experts. It might be an easy fix, like too-warm pajamas. But if you’re sweating through your sheets every night regardless of what you wear to bed, it could be time to talk to your doctor.
“When you sweat while you’re sleeping, your body is losing water while it should actually be in a state to conserve fluids since you don’t have any fluid intake at night,” explains sleep scientist Roy Raymann, Ph.D., chief scientific officer at SleepScore Labs. “While some minimal perspiration is normal at night, sweating that can be easily noticed or even wake you up from sleep might need some special attention.” You may have sleep hyperhidrosis—the medical term for excessive night sweating.
Below, we asked the experts to help us map out common causes of night sweats so you’ll never have to ask yourself “Why do I sweat when I sleep?” again.
It’s your pajamas.
The first thing to do is check your pj’s, says Michael Breus, Ph.D., a sleep specialist and author of Good Night: The Sleep Doctor’s 4-Week Program to Better Sleep and Better Health. Are they made of polyester, a fabric that can contain body heat? What about socks? They can trap extra body heat.
What to do about it: Take your socks off and switch to a lighter, more breathable fabric like cotton. (Or if you’re up for it, try sleeping in the nude.) Breus also recommends Cool-jams moisture-wicking pajamas. “I use them when I travel, when it’s less easy to monitor the temperature in a hotel room,” he says. “They work well.”
The room is too warm.
This may be stating the obvious, but your bedroom should feel comfortably cool. “The optimal bedroom temperature is around 65 degrees Fahrenheit,” Raymann advises.
What to do about it: The solution here is straightforward: Lower the temperature in your room. About 30 minutes before you go to bed, crank the thermometer down to 65. If that’s still not enough, add some air flow. “A box fan or an overhead fan is definitely helpful to get a cooler breeze going over the body,” Breus says.
Your bedding or mattress aren’t a fit.
It’s very likely you and your partner have different sleep needs, Raymann says. If you’re sweating, it might be because the comforter or mattress that keeps your partner perfectly comfortable is too insulated for you.
What to do about it: If it’s just you in bed, the fix is simple: Get a mattress and bedding with low insulation. If you share with a partner who runs cold, look for a dual-zone comforter that has different levels of insulation on each side. Breus also recommends trying products like chiliPad, a pad that goes under your sheet and can run cool or warm.
You hit the gym too close to bedtime.
Regular exercise is great for sleep but not if you do it too close to bedtime. “During exercise, your body warms up,” Raymann says. “For sleep, your body needs to get rid of that extra heat.”
What to do about it: Schedule your workouts for the morning or afternoon hours, if your schedule allows. If you are going to do an evening exercise class, opt for something gentle like yoga that won’t raise your core temperature as much.
You had a late-night meal.
Those nachos may look good, but they can also cause night sweats—spicy meals can trigger a sweat response, Raymann says.