Cool Mist vs. Warm Mist Humidifier: Which One Is Best for You?

Is dry air making your skin itchy and your throat scratchy? Cool mist or warm mist humidifiers can provide relief by adding moisture into the air around you. But they aren’t perfect — they can also harm your airways and lungs if you’re not careful.

Here’s what you need to know about cool mist versus warm mist humidifiers, including their risks and benefits, how to care for them, and how to prevent mold from building up inside of them.

What does a humidifier do?

A humidifier is a device that adds moisture to the air. 

Humidifiers can help when temperatures drop and the air is particularly dry. Dry air can cause your nose to get crusty and bloody. Or it can irritate a sore throat or chapped lips. Humidifiers can ease these issues as well as respiratory problems, like cold and flu symptoms and allergies.

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Does a humidifier help with coughing or congestion?

Yes, humidifiers can help with many cold and flu symptoms, including cough and congestion. A cough can be caused by things like dry air, chest congestion, or postnasal drip. 

By adding moisture to the air, humidifiers can help loosen chest congestion and soothe scratchy throats from things like postnasal drip. The mucus formed in your nose and sinuses might be thick and sticky when the air is dry. Adding moisture to the air will help thin out that mucus, so your respiratory passages are easier to clear. Humidifiers can’t cure you of a cold or flu, but they can help you feel better as you recover.   

Does a humidifier help with other health problems?

Maybe. Although the full effect of in-home humidifiers is still being worked out, research suggests that using a humidifier might help by:

• Relieving dry skin, including eczema

• Preventing dry eyes 

• Reducing the spread of respiratory viruses like influenza or COVID-19

What are the differences between a cool mist humidifier and a warm mist humidifier?

Cool mist humidifiers release cool moisture into the air. They use ultrasonic vibrations or a rotating disk to break down water into tiny droplets. These droplets get dispersed into the air. 

Cool mist humidifiers seem to work well for opening up swollen nasal passages.

Warm mist humidifiers, or vaporizers, release warm moisture into the air. They either evaporate water through an absorbent filter or they warm water with a heating element that releases steam.

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“Cool mist humidifiers can also offer soothing relief when the airway feels inflamed while a warm mist humidifier might help break up mucus like steam does," said Neeta Ogden, MD, a medical spokesperson for the Asthma and Allergy Foundation of America (AAFA).

But they’re equally effective at offering relief from cold symptoms, such as:

• Chest congestion

• Sore throat

• Dry skin

• Chapped lips

• Coughing

Dr. Ogen said that both effectively add humidity to the air and equally address these symptoms. “It’s really more a personal preference of what feels better.”

What are the pros and cons of cold mist vs. warm mist humidifiers?

The benefits of warm and cool mist humidifiers are similar, but they have different downsides to consider.

Pros of warm and cool mist humidifiers

Warm mist and cool mist humidifiers both ease cold and flu symptoms and dry skin.

"Both types of humidifiers effectively moisturize the airway and promote the effectiveness of our cilia (hairlike structures), which beat away allergens, irritants, bacteria, and viruses,” Dr. Ogden said.

And, according to Consumer Reports, cool ones start as low as $19 and warm ones at $15, making them both affordable.

Cons of cool mist humidifiers

Here are the cons you should consider about cool mist humidifiers. They:

• Can disperse disease-causing organisms into the air

• Can spread minerals and white dust if you fill with hard tap water

• Must be sterilized or disinfected often

• Can become contaminated after the first use

• Can be difficult to clean and decontaminate

• Can cause diseases like hypersensitivity pneumonitis and humidifier fever

• Should be filled with distilled water, which can get expensive

Cons of warm mist humidifiers

And here’s what to consider with warm mist humidifiers:

• They can scald pets or children if left unattended.

• Filters can get dirty quickly and may need to be replaced often.

• Warm steam can promote the growth of dust mites.

• The American Academy of Pediatrics doesn’t recommend heated humidifiers for homes with young children.

How and when to use a humidifier

Humidifiers are great tools for easing symptoms like cough and congestion. You can also use a humidifier in dry climates to moisturize dry skin and chapped lips.

Like with any electrical appliance, there are some best practices on how to use warm and cool mist humidifiers:

• Use distilled or demineralized water.

• Avoid using a humidifier in enclosed spaces.

• Don’t add vapor rubs or essential oils to your unit.

• Clean and refill with clean water daily. Use a brush or scrubber to remove film or buildup in and around the tank. (And make sure to unplug the unit first.)

• Use the cleaners and disinfectants recommended by the manufacturer.

• Dry the device both inside and out thoroughly after cleaning.

• Keep warm mist humidifiers out of reach of children and pets.

• Don’t let walls and carpeting around the humidifier get damp.

• Drain and clean the tank before you store it and when you take it out of storage.

Is it OK to sleep with a humidifier every night?

Depending on your needs and the humidifier, you may be able to use it every night. Dr. Ogden recommends daily use of cool mist humidifiers to many of her clients. You can run them only while you sleep or all day if you prefer.

“Certainly, you can run it 24 hours a day for the added benefit of keeping the air in the room less dry,” she said. As long as you clean and disinfect your humidifier regularly, you should be OK.

If you use a warm mist device, Dr. Ogden recommends getting a hygrometer, a humidity monitor. You can find one online or at your local hardware store.

“Make sure the room humidity stays below 50% to keep dust mite growth at bay,” Dr. Ogden said. Higher levels of humidity can also lead to mold and mildew. 

But as long as the humidity in the room stays below 50%, you can use a warm mist humidifier nightly.

Can a humidifier make you sick?

Yes, a humidifier can make you sick. Bacteria and fungi like mold can grow in the tank and release dirty mist into the air. Breathing in dirty mist can cause flu-like symptoms, infections, and other lung problems. Humidifier fever, for example, can be caused by microorganisms in a home humidifier. 

Humidifiers can also worsen allergy and asthma symptoms. They do so by spreading dust mites, which can aggravate someone with indoor allergies or asthma.    

How do you prevent mold from growing in your humidifier?

Both warm and cool mist humidifiers can get moldy. “If they’re not cleaned properly, they are a breeding ground for mold and bacteria, and then you’re inhaling mold spores,” Dr. Ogden said. Breathing in mold can cause lung problems or worsen asthma or allergy symptoms.

The key to preventing mold is to clean and disinfect regularly. Use the products the manufacturer recommends to keep film, scum, and crust at bay. If they recommend bleach or other harsh cleaning products, make sure to rinse the tank well. This is to avoid breathing in harmful chemicals.

Many manufacturers suggest vinegar for disinfection. Vinegar may have a strong smell, but it won’t hurt your lungs, and rinsing well should keep the smell to a minimum.

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Written by:

Ana Gascon

Ana Gascon has over 15 years of writing and editing experience, with 8 years in health and medical content work. She is a versatile health and medical content creator who writes about acute conditions, chronic diseases, mental health challenges, and health equity.

Edited by:

Alex Eastman, PhD, RN

Alex Eastman, PhD, RN, is a California-based registered nurse and staff medical editor at GoodRx, where he focuses on clinical updates and Latino health.

Reviewed by:

Kerry R. McGee, MD, FAAP

Kerry McGee, MD, FAAP, has over a decade of experience caring for babies, children, and teenagers as a primary care pediatrician. She has a special interest in adolescent health, particularly in adolescent mental health.

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