If you’ve used the internet at all since the first hint of chill hit the fall air, you might well feel like the world is screaming at you to get a certain device that’s essentially a seasonal miracle worker: a humidifier. The little jugs of wonder that emit either cool or warm mist are the keys, it seems, to getting your life in order once your heat kicks on. Dry skin? Your humidifier can help fix that! Can’t kick a drippy case of the sniffles? Yep, your good ‘ole humidifier is here to help. Adding in the humidity that your furnace saps from the air is, in fact, insanely beneficial for your sinuses, which tend to take a hit in colder temperatures.

But all of this goodness can get wiped away if you don’t take proper care of your device. Without taking the time to regularly clean and maintain your humidifier, you’re essentially self-subscribing to a world of (sinus and dry-skin) pain more severe than what you might have dealt with sans device. Since the star ingredient is water, these tools—like essential oil diffusers—can easily develop mold, mildew, and bacteria.

“There are definitely health issues that can crop up from using a humidifier that has developed mold or mildew or bacterial contamination, dermatologist Jessica Krant, MD, MPH, tells WebMD. “Itchy skin rashes and itchy eyes could be a sign of mold or mildew allergy coming from the humidifier.”

Since the star ingredient of a humidifier is water, it can easily develop mold, mildew, and bacteria.

While, as Dr. Krant says, mold and mildew can cause irritation in the eyes and skin, an itchy nose and throat are also symptoms of mold exposure. And since you bought your humidifier to relieve these sorts of things, it’s pretty counterintuitive that you’d be tasked with combatting them because of your device, right?

Luckily, there’s an easy fix: Just clean the darn thing! Each humidifier should come with a care guide that tells you how, exactly, to properly maintain your humidifier. But if you tossed it during your KonMari phase (no judgment—info leaflets rarely spark joy), here’s a handy little guide: Empty the water tank at least once a day, and refill it with fresh H20. Then, once a week, make sure to clean it out with some water and white vinegar.

Aside from that, it’s smart to give it a good scrub and allow it to dry out before you store it for the season. And if you’re just about to use it for the first time of the year, do the same. Mold or mildew may have snuck it while the trusty sucker was hibernating. Follow these steps, and your humidifier will work perfectly all chilly season long.

Other tried and true ways to boost immunity? Chicken noodle soup and certain essential oils.