Humidifier vs. Purifier: We Asked Medical Experts Which Is Better for Allergies

CNET

03-06-2025

Spring is a common time for both indoor and outdoor allergies, which makes it essential to take measures that can make your environment as healthy and safe as possible.
There are a few home tech gadgets to consider when trying to protect yourself from indoor allergies. We spoke to allergy and medical experts, and they both say an air purifier or humidifier can be effective. Humidifiers, though, if used improperly, can cause more harm than good. "If there is too much humidity in a room, it can promote the growth of dust mites and mold," said Brian Greenberg, an allergist, immunologist and scientific advisor to 1MD Nutrition.
"Air purifiers filter the air of allergens, so they are more effective at reducing and preventing allergy symptoms," says Dr. Purvi Parikh, an allergist with Allergy and Asthma Network.
Here's what you need to know.
Air purifiers vs.Air purifiers and humidifiers work in very different ways. Air purifiers are generally considered very helpful for environmental allergies.
"In general, air purifiers work by taking air in through a variety of filters and then sending it out particle-free. There are five basic types of filters -- electrostatic, ionizer, ozone, UV and HEPA. HEPA air purifiers are the most effective and are made by a wide range of companies," said Dr. Greenberg.
The better the filter inside the air purifier, the stronger the airflow and the more the filter can remove from the surrounding environment. Typically, these filters need to be replaced or cleaned periodically for optimal function and to notice a substantial reduction in allergy symptoms.Humidifiers are devices that either boil water or spray a fine mist of water into the environment in small droplets or vapor so that the air has a higher moisture level. Those who suffer from allergies often experience uncomfortable nasal passages and itchy eyes anyway, and dry air can exacerbate these feelings, as well as trigger asthma symptoms and eczema. For this reason, people living in dry environments sometimes experience symptom relief when they incorporate a humidifier into their environment.
Do air purifiers really help allergies?
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Air purifiers have been studied and found effective at reducing some indoor allergens. "Air purifiers filter the air of allergens, so they are more effective at reducing and preventing allergy symptoms," says Dr. Parikh.
The key metric to consider is the total size of the space relative to the recommended size for the air purifier for allergies that you've chosen. A small desktop purifier may have a negligible impact on a large open-plan office. Still, a robust air purifier in each room where you spend time can keep the space's particulates down to a noticeable degree if you have indoor allergies. It's also worth making sure that you place it in the best location for an air purifier where you'll benefit from it most.
An excellent first step is to consider the space where you typically suffer most from indoor allergies, such as the bedroom while sleeping. Try an appropriately sized air purifier with a HEPA filter with the doors closed in that space for a few nights when you typically have indoor allergies, and see if your breathing and other symptoms are improved.
At a minimum, air purifiers don't have any significant downsides, though some can emit a noticeable sound.
Would a humidifier help with allergies?
Humidifiers add moisture to the air, either by heating water to create steam (often called a warm mist humidifier) or by spraying tiny droplets of room-temperature water into the air (often called a cool mist humidifier).
"In extremely dry climates, that can be helpful to moisten the mucous membranes of the respiratory tract, preventing dryness and irritation," explains Dr. Greenberg. "They can, however, create some issues. If there is too much humidity in a room, it can promote the growth of dust mites and mold. And, the water chamber itself needs to be cleaned out daily; otherwise, it can become a mold reservoir."
In general, humid air makes things like mold and mildew more likely to grow, meaning that a humidifier may actually make indoor allergies worse if you boost the humidity of the space too high. If you are choosing a first step for reducing indoor allergy symptoms, an air purifier will be a lower-maintenance solution. Adding a humidifier can help in very dry environments but requires some maintenance to avoid growing additional allergens.
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If your indoor allergies have been tied to mold, you can still use a humidifier with these precautions:
Most humidifiers designed for home use need to be cleaned weekly, with the water chamber itself emptied daily if all the water isn't used. This can be done according to the instructions that come with your humidifier, though many people use a weak acid like vinegar to remove mineral buildup and discourage growth in the humidifier's parts.
On a monthly basis, it's recommended to do a full disinfecting cycle, like a scrub with a bleach solution or hydrogen peroxide. Time this cleaning cycle such that you never mix vinegar and bleach, making a dangerous chemical reaction you do not want to breathe.
Consider using distilled water to discourage growth and mineral deposits on the humidifier that can be hard to clean.
Give humidified areas in your home a chance to "dry out" between uses. If you use a humidifier to sleep during allergy season, for instance, you risk less mold growth if you let the humidity drop during the day by leaving the humidifier off and the door open to the rest of the home.
The best solutions for indoor allergiesMinimizing indoor allergies doesn't stop at adding a humidifier or air purifier. Some major benefits can be gained by modifying your indoor environment in other ways:
If you have central heating and cooling, checking and changing your filter every month removes some allergy-inducing particulates, reducing how hard your air purifier would need to work and making your air conditioner more efficient at the same time.
Don't underestimate the impact of regular cleaning practices. "Wash your bedsheets once a week in hot water, clean and vacuum one to three times per week," said Dr. Parikh. She also mentions that keeping vigilant about leaks can prevent mold growth, and removing rugs and carpets in favor of easy-to-clean hard surfaces can further lower allergens.
Keeping the windows closed during high pollen season can reduce pollen allergies, and keeping pets out of sleeping areas can help prevent pet-dander-related allergies at night.
Encasing mattresses and pillows can discourage mold and dander from getting trapped in these upholstered materials, releasing them into your sleep air space. The Asthma & Allergy Friendly certification offers suggestions on air cleaners, filters, bedding options, and encasings that meet independent testing standards. Still, many other brands also exist that can help you reduce exposure to allergens in your mattress and pillows.
According to Dr. Parikh, putting stuffed animals in a high-heat dryer for 20 minutes every week can diminish microbial growth and reduce allergen potential for children who play with them.
Expert allergy tips
The same behaviors that boost your immune system in other contexts can also be helpful for environmental allergies. Good sleep, regular exercise and eating a healthy diet rich in fruits, vegetables, whole grains and lean proteins will only benefit your indoor allergy journey. That being said, some allergens generate a strong response even in people who have taken appropriate steps to boost their immune system's health.
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Some people find that, if they aren't allergic to common house plants, adding indoor plants helps keep the air fresh in their homes.
Environmental changes, as mentioned in this piece, are a major factor in reducing indoor allergies, but medical treatment can also help.
"If you're very allergic, allergen immunotherapy (allergy shots) with a board-certified allergist may be a great treatment for you to desensitize yourself to your indoor allergens and thus become less allergic over time," said Dr. Parikh.
Talk to your medical professional about whether your particular allergies are likely to respond well to allergy shots and whether that's the best next step.
The bottom line
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If you suffer from indoor allergies, it's wise to experiment with environmental changes that can reduce symptoms or help your medication more effectively reduce your suffering during particular times for springtime allergies. Air purifiers can have a positive impact, reducing total particulate matter in your air if you size them appropriately to your space and opt for a highly effective filter like a HEPA filter.
Humidifiers and allergies are a more complicated combo, with careful use potentially reducing the dry airway symptoms brought on by very dry environments. Casual use of a humidifier without proper maintenance can potentially increase humidity to the point where mold and dust mite growth increases. Failing to clean a humidifier properly can put minerals and mold spores into your air. With proper maintenance and an eye to reasonable humidity, however, even a humidifier can help mitigate the impact of indoor allergens.