Air purifier vs humidifier: Which is best for seasonal allergies?

Here's a breakdown of key differences between an air purifier and a humidifier, as well as tips for using them both this allergy season.

My pollen allergies have gotten much worse over the last three years, causing me to spend a couple months each spring and fall with watery eyes and congestion (despite taking medication). Cycling through Central Park in the spring when cherry blossom trees are at their peak is a gorgeous experience for some, but for me, the beautiful blooms mean I emerge a sniffling, sneezing, watery-eyed mess.

And it's not just me feeling like my allergies have gotten worse: According to researchers at the University of Michigan, climate change and a warmer planet means allergy seasons may be longer. A 2022 study published in Nature Communications found that annual pollen counts could rise by 200% or more by the end of the century. The research also documented that tree pollen releases have begun to overlap, meaning a higher concentration of pollen is in the air at any given time.

If you, too, suffer from allergies like mine, you may be wondering what you can do about the air quality inside your home. You’ve likely heard about both air purifiers and humidifiers in reference to managing allergies, but which one actually works best?

To find a science-backed answer, I got in touch with Melanie Carver, chief mission officer for the Asthma and Allergy Foundation of America (AAFA), and Dr. David Gudis, chief of rhinology and anterior skull base surgery at Columbia University Vagelos College of Physicians and Surgeons.

Carver said that in addition to the air purifiers and humidifiers we usually hear about, there are also air cleaners. All of these appliances function in different ways, though purifiers and cleaners are similar.

She explained that air cleaners use filtration to remove allergens and other particles from the air, while air purifiers sanitize the air. So, for allergies, "you’ll want a high-quality air cleaner that captures allergens such as pollen, animal dander, dust mites, or mold spores."

Put another way, air cleaners pull air into a machine, where it goes through filters that trap airborne irritants and scrub it free of said irritants. Meanwhile, air purifiers use ozone, ionizers, or UV light to kill microorganisms.

Humidifiers, in contrast, put moisture into the air via a reservoir that transforms water into mist, then expels it into the air. Both humidifiers and their air cleaner and air purifier cousins have benefits when it comes to managing allergies, and many people use them simultaneously.

As for the question of what's best for dealing with allergies, the verdict lands on the side of air purifiers and cleaners — ideally ones that comply with AAFA certification.

Air purifiers or cleaners are better for allergies because their actual function is to sanitize or remove allergens in the air. Most have high efficiency particulate air (HEPA) filters that capture particles as small as .3 microns. They work to remove dust, bacteria, mold, pollen, and pet dander from the air.

"Air purifiers are extremely helpful for reducing unwanted allergens and air particles in the home," says Gudis.

However, how efficacious the air purifier actually is depends on how you use it. Air purifiers are made to operate in enclosed spaces, meaning that they’re not very efficient when the windows are open. Carver also pointed out that air cleaners won't work if indoor air is too humid.

Furthermore, purifiers and cleaners require some maintenance: Make sure to replace or rinse the filter as directed by the manufacturer to ensure the unit works effectively and lasts for years to come.

The best air purifiers cover large areas with silent operation and have, at the very least, a true HEPA filter. Some have a three- or four-stage filtration system to remove a high amount of contaminants in the air.

When deciding what air purifier to get, Gudis pointed out that different-sized rooms require filters of different capacities. Most air purifiers and their filters indicate what square footage of space they’re appropriate for use in. And while HEPA filters vary in fanciness, even the most basic HEPA filters are better than having nothing to filter your air.

"Some HEPA filters," he continued, "have additional functions, like cooling, measuring carbon monoxide levels, and humidity levels as well. But even the most inexpensive HEPA filters can dramatically reduce the level of airborne allergens, so there is no need to exceed your budget for the extra bells and whistles that you do not need."

AAFA recommends portable air purifiers that include picks from Dyson, LG, and Rabbit to help manage airborne allergies and asthma.

Dyson Purifier Cool TP07 Smart Air Purifier and Fan - $590 at Amazon

With a fully sealed HEPA H13 filter, this Dyson automatically senses, captures, and traps particles — plus reports pollution in real time via the MyDyson app. It has a fan/cooling mode for a little chill without totally turning on the AC and works with Alexa, Siri, and Google Home.

LG Puricare 360-Degree Air Purifier - $1,100.78 at Amazon

The futuristic-looking LG Puricare cleans up 512 square feet of air. It has tilt and rotate capabilities to evenly distribute the air and a clean booster to push air up to 24 feet. Given the price tag, you’d hope it's quiet, and it is: It operates as low as 25 decibels. For the tech-centric, the device is compatible with LG SmartThinQ as well as Alexa and Google Home.

Levoit Core 400S Air Purifier - $299.99 at Amazon

The Levoit has a three-stage filtration process including a pre-filter, a HEPA filter, and a carbon filter to neutralize odors. It purifies 403 square feet five times per hour and 909 square feet two times per hour, giving you consistently refreshed air. Plus, it works with Alexa.

Humidifiers do not remove allergens from the air, but instead add extra moisture to an interior environment, which can help soothe irritation caused by dry air. So, if you live in a dry climate, humidifiers can help reduce symptoms like itchy nose, eyes, throat, rhinitis, and breathing difficulties.

"The goal is to keep humidity between 30% and 50%," said Carver. She suggests that those wanting to measure it purchase a hygrometer.

The Environmental Protection Agency (EPA) recommends using water with low mineral content (like distilled water) to stop minerals from releasing into the air, and to make sure the tank is wiped down and refilled daily to help prevent the growth of microorganisms that could further trigger allergies.

Dyson 303516-01 AM10 Humidifier - $518.99 at Amazon

This AAFA-certified humidifier from Dyson distributes humidified air evenly while killing 99.99% of the bacteria in the water with ultraviolet cleanse technology. It accurately measures temperature and humidity and makes adjustments providing you a comfortable environment.

Beyond getting an air purifier or cleaner, there are other steps you can take to keep allergens out of your home, said Gudis — like showering before bed.

"Otherwise, all of the pollen and allergens that accumulate on your hair and skin all day long will end up on your pillow and sheets, and you’ll be rolling around in them all night," he said.

Also vacuum carpets and rugs, wash clothes, and groom pets more frequently during allergy season. "It's very helpful to keep the windows closed and use air conditioning during the weeks of high pollen levels as well," Gudis added.

Being able to breathe easily through your nose is one of those things you take for granted until you can't. An air purifier or cleaner means that at least you’ll be breathing easier at home — and, hopefully, sleeping a little sounder too.