Did you know that humidity plays a role in virus transmission, and higher levels of humidity can reduce the amount of aerosalized virus (like the flu) in your home when it’s spread through coughing? A humidity level greater than 40% in your home or office can reduce influenza’s ability to spread significantly (1).
It’s winter, and there is no shortage of nuisances related to cold, dry air! From dry skin to nasal congestion, coughs that won’t quit, static electricity, and a viscous cycle of indoor heating which makes our air even drier—some of us are lacking humidity.
Adding humidity to the home, especially during times of illness, has been a traditional remedy which has sent many of us to keep pots of water boiling on the stove, fogging up our bathrooms with hot showers, and hiding ourselves under towels while breathing in the steam from a hot bowl of water. Humidifiers are an easier way to quench our need for moisture, but they are generally under-utilized and neglected because of their maintenance.
Humidifiers can be an asset to your health when cleaned, maintained, and chosen properly. They come in all shapes, colors, and sizes. It can be confusing when determining which type of humidifier you should choose (warm mist versus cool mist), what type of cleansing agent should be used, and even what type of water should be used.
Below, we explain which humidifiers may help more with allergies, colds, and the flu; the different types of humidifiers in both the cool and warm mist versions and their pros and cons; safety and cleaning; and take a look at some of the best humidifiers available for specific needs.
Cool Mist Humidifiers vs. Warm Mist Humidifiers
Both cool mist humidifiers and warm mist humidifiers turn water into vapor which circulates in the ambient air. There are humidifiers meant for personal use (which are best used on desks or on nightstands next to beds), larger ones meant for entire rooms, and commercial ones (which are sometimes installed alongside heating and cooling units for businesses, factories, or hospitals).
If you think you might have need for both types of humidifiers, there are some units which combine them and let you choose which setting to use.
Whether you choose a cool mist or a warm mist humidifier, it’s best to use distilled or demineralized water (emptying any reservoirs of water daily), and clean the unit once weekly according to manufacturer directions (they will also specify what you should use to clean it, from soap to bleach to vinegar). Some units contain filters which should be changed according to the manufacturer, or absorbent wicks which should also be changed according to the unit’s directions.
Warm Mist Humidifiers
- Best for cold symptoms
- Doesn’t hold standing water
- Contains a heating element, hot water, and hot steam and is not recommended for unsupervised use around children due to risk of spills and burns
- May be noisier
- Can warm up room; good in winter, but hard to use in summer/humid climates
- Some units have filters which need to be replaced—we’ve recommended a filter-free unit below
If you’ve used any of the methods listed above—boiling pots of water, fogging up the bathroom with the shower, inhaling a bowl of hot water—then you’re familiar with the warm mist which steaming water produces. This is the same type of vapor that you will get when you use a warm mist humidifier, because it contains a heating element which will boil the water before it releases the mist into your environment.
The mist feels warm and can produce a warm, humid environment (similar to the way a steamy bathroom feels), but by the time it reaches you and your lower airways, it will have cooled down and is no different than the type of mist produced by a cool mist humidifier.
Best Warm Mist Humidifier
“Good Housekeeping: 5 Top Humidifiers to Buy in 2019”
Cool Mist Humidifiers
- Best for providing general humidity, better sleeping and less snoring, protecting hardwood floors and plants from dry air
- Does not contain hot water or steam and is safe for use with children
- Quiet enough to use at night while sleeping
- Can cool down a room; good in the summer
- Requires a little more maintenance due to a reservoir with standing water which must be cleaned weekly in order to not build up harmful bacteria and fungus
In contrast, a cool mist humidifier does not contain a heating element, and the mist released from these units feels cool to the touch (similar to a swamp cooler or evaporative cooling unit). They come in two forms: evaporative or ultrasonic.
- Evaporative Cool Mist Humidifier: This type of humidifier uses an evaporative process in which a wick filter soaks up the water and a fan blows air from the room past the filter, and the water evaporates and is released into the air as an invisible mist. This is the least likely type of cool mist humidifier to release airborne bacteria (Consumer Reports, 2018).
- Ultrasonic Cool Mist Humidifier: Using ultrasonic technology, ultrasonic waves vibrate water through a nebulizer and aerosolize the water into an ultra-fine mist.
Best Evaporative Cool Mist Humidifier
Quiet Mist Humidifier, Humidifier for Bedroom, Waterless Auto-off, High Low Mist, Night Light, Baby Kids Nursery, Filterless Humidifiers, 2L Tank, ETL Approved
Best Ultrasonic Cool Mist Humidifier
Top-Fill Design, Ultrasonic Tech operates at a near-silent 28 dB, Safety Automatic Shut-off, 3 Mist Modes, Upgraded Filter Core
Best Cool Mist & Warm Mist Humidifier Combination All-in-one
Whisper-Quiet Operation, 4.5L/1.2 Gallon, LED Touch Display and Remote Control
When should you use a cool mist versus a warm mist humidifier?
Since both types of humidifiers are releasing moisture into the air, they will benefit the user looking for more humidity in their environment, but certain types of illnesses or conditions are better suited to one kind of humidifier.
For Allergies or Asthma:
Warm or cool humidifier? It depends.
Seasonal allergies can be improved with humidifiers because they can help open up nasal passages and reduce inflammation so you can breathe better. Keeping your nasal passages moisturized can also make it easier for you to shed any allergens that may stick to your nasal passages and cause irritation and inflammation.
Different types of allergies will require different types of humidifiers. Increasing the humidity can also cause a different set of problems—and allergies—to occur. A common cause of indoor allergies is dust mites, and they prefer more humid environments (around 40-50% humidity). You may be suffering from seasonal allergies and decide to try a humidifier, which has the possibility of increasing the levels of dust mites in your home, giving you another allergen with which to contend.
Like dust mites, mold allergens can also be caused by humidifiers, due to the conditions in which mold grows (in areas of high humidity and moisture). Mold allergens can be reduced by proper maintenance, cleaning, and using the right type of water in the humidifier, but it’s a consideration that those who are more sensitive to these types of allergens should consider (3).
Finding the right balance of humidity in your home will relieve symptoms but not be so high as to cause the growth of dust mites and mold. You can monitor the amount of humidity inside your home with a hygrometer (a device, similar to a thermometer, that measures the level of moisture in the air). The ideal indoor humidity level is 30-50% (4).
If you are already dealing with allergies or asthma, it’s best to check with a doctor before you use a humidifier due to the complex nature of allergies and the possibility that dirty humidifiers can make existing allergies worse or cause new ones to occur.
To eliminate the threat of mold in the home, choosing a warm mist humidifier can be a good solution because it boils the water and should reduce the amount of bacteria and fungus that could build up inside the unit. Warm mist humidifiers also do not retain a standing pool of water (unlike cool mist humidifiers which do keep a reservoir filled with water).
For Colds or Flu:
Warm or cool humidifier? Warm for adults—cool mist humidifier for children.
If you’re all stopped up and congested, a warm mist humidifier can thin the mucous that’s stopping you up, especially if you’ve got a cough.
Once you’ve chosen a humidifier and committed to the unit maintenance and cleaning, you can enjoy all the benefits of clean, soothing air.
1. Noti, John D., et al. “High Humidity Leads to Loss of Infectious Influenza Virus from Simulated Coughs.” PLOS One, 27 Feb. 2013, doi:https://doi.org/10.1371/journal.pone.0057485.
2. Farrell, Mary H.J. “Why You Should Clean Your Humidifier.” Consumer Reports, 1 Feb. 2018, https://www.consumerreports.org/humidifiers/why-you-should-clean-your-humidifier/.
3. “HUMIDIFIERS AND INDOOR ALLERGIES.” American Academy of Allergy Asthma & Immunology, https://www.aaaai.org/conditions-and-treatments/library/allergy-library/humidifiers-and-indoor-allergies.
4. “Humidifiers: Air Moisture Eases Skin, Breathing Symptoms.” Mayo Clinic, https://www.mayoclinic.org/diseases-conditions/common-cold/in-depth/humidifiers/art-20048021.
5. Hoecker, Jay L. “When Should I Use a Cool-Mist Humidifier versus a Warm-Mist Humidifier for a Child with a Cold?” Mayo Clinic, https://www.mayoclinic.org/diseases-conditions/common-cold/expert-answers/cool-mist-humidifiers/faq-20058199.