Should I Have Houseplants If I Have Asthma?
The only houseplant I own is not even a plant, exactly. It’s a cactus, her name is Marge, because when I got her as a birthday present several years ago, it looked like Marge Simpson, so it became she and she became Marge.
However, sometimes I peruse through the tips in my Atmotube air quality monitor app*, and in the “Simple steps to reduce VOC levels” area it tells me to get some houseplants. Except, I sort of fear I’d just quickly kill houseplants because I never drink water myself and sometimes forget to eat food, so what luck would a plant have? Also, even if plants absorb volatile organic compounds in your house and maybe help maintain proper humidity, are they even a good idea if you have asthma?
What plants are good at—and what they aren't
Plants make rooms look nice in catalogs and stuff, and I recall from somewhere they’re good for your mental health, but clearly that’s if you don’t kill them (thus why I own a cactus).1
When it comes to asthma, of course, there are other questions: my main one would be: will a few plants help raise the chronically low humidity in my house to a level that is a bit more ideal? Do they cause problems with mold or pollen if you have allergies? Do they really filter that many VOCs or absorb that much carbon dioxide to be useful?
So let’s take that one step at a time.
A study about houseplants improving indoor air quality focused around CO2 and humidity placement of 5 Spathiphyllum wallisii ‘Verdi’ or Hedera helix plants in a room with uncovered soil could raise room humidity from 40% to 60%.2 Generally it’s considered for this same range of relative indoor humidity levels to be helpful to a human's health.2 However, this seems to be based on calculations, not an actual measurement.
CO2 - carbon dioxide
The above study about houseplants improving indoor air quality focused around CO2 and humidity states it was demonstrated that “little potential is offered” by the studied plants to reduce CO2 if in a low light environment—like most homes. If the light is increased, more carbon dioxide would be absorbed by the plants. However, it might not be as appealing for humans who have to live in the shared environment to be under super bright lights all day!
It’s also noted that of the low-light plants—both the ones mentioned above in the humidity section, as well as Spathiphyllum wallisii ‘Bellini’—would require a ridiculous number of plants to “see any significant CO2 concentration reduction."2 Okay they said “unrealistic,” not “ridiculous,” but same thing.
Look, my friend wants to fill her Animal Crossing house with succulents. But there’s probably a reason she hasn’t done this in her real house.
Basically, it’s unrealistic to think your house will be plant-y enough to reduce CO2 enough to neutralize your exhalations while also remaining habitable and not living in the equivalent of the tropical house at the zoo.
If, like me, you don’t grow plants indoors, you may not know they can grow mold. It was just something I’d heard about before in passing and went into the back of my brain but I didn’t know why. “Indoor Plants for Beginners” may not be the most scientific source, but it broke things down for me: indoor plants can grow mold on the plant or the soil if they get adequate sunlight, too much water, their pot doesn’t drain well enough, or the area they are in is poorly ventilated.3 If you have a mold allergy, that means keep a close eye on your plants, get rid of any molding plant parts or soil quickly (moldy soil may appear “dusty” or more obviously moldy, apparently)—or, keep your plant growing outside.3
It probably goes without saying, but if you have pollen allergies, you’re probably not going to want your indoor plant growing to include flowers or other pollinating plants or trees. There are even books about allergy-friendly or “allergen-free” gardening—but it’s likely a simple google search tailored to your own needs will help you determine what is best for you.
So let’s get this out of the way first: if you want plants to act as air purifiers, that’s just not a thing research supports.4 Kinda like CO2, you’re just never going to get enough filtration to “clean” your air from a reasonable number of plants. So, if you want more information about volatile organic compounds, I wrote an article about VOCs here.
House plants for asthma: Rooted in a lack of evidence?
The take-home message is: buy some plants if you like them and you’re confident they’re not going to induce allergic reactions, immediately or in the future. Don’t buy plants if you think they’re going to improve your air quality or even asthma symptoms—because research seems to indicate they won’t. And if you do buy indoor plants, do your research!
*Disclosure: I received the Atmotube for free to review on my blog. I note this only in full disclosure, not because it has anything to do with this post. In fact, I only thought to write this post because I saw a picture of a plant on a catalog and that is how my brain jumps to ideas apparently, in case you were wondering.
Have you developed a new food allergy in the last 5 years?