My Mother-in-Law’s Strange Houseplant Pest Hack Uses a Common Cough Remedy – and I Was Skeptical Until I Tried It

I thought I had finally won the war on fungus gnats. After getting through a bumper pack of sticky traps and rigidly bottom watering for months on end, I realized I couldn’t recall the last time I had seen one of those tiny flying gremlins. Peace had returned to my houseplant jungle. But not long after I breathed a huge sigh of relief (without getting one stuck in the back of my throat), my mother-in-law brought me a Thanksgiving cactus.

She had grown it herself from cuttings taken from her own plant, which I must say is an absolute showstopper that blooms over the holidays and again in spring. It was an undeniably thoughtful, lovely gesture, and I was very happy to accept it – until, a couple of weeks later, I noticed that unmistakable flutter. In true Trojan Horse style, the fungus gnats had invaded again.

On her next visit, I gently explained the situation to my mother-in-law, and she didn’t argue. Apparently, she had been dealing with her own infestation, which she quickly nipped in the bud. “You should try Vicks!” she suggested. After my initial confusion, I soon established that she was talking about Vicks VapoRub. Apparently, a friend of hers has been rubbing a little of this old-school cold and flu remedy around her plant pot rims for decades to deter fungus gnats and other common houseplant pests, such as aphids and whiteflies. She swears by it, and my mother-in-law became an immediate advocate.

How the Vicks VapoRub Hack Works

The hack is simple: take a small amount of Vicks VapoRub – available in bulk on Amazon, along with this more affordable own-brand product – and rub it around the rim of the pot. Avoid getting it in the soil or on the plant itself, as it could harm plants – you just want a thin layer along the pot edge.

Vicks contains several strongly scented compounds that are known to be irritating or disruptive to insects, most notably menthol, camphor, and eucalyptus oil. It also uses petroleum jelly as a base ingredient, which makes the ointment stick to surfaces when applied. Fungus gnats, like many small flying pests, rely on scent to find suitable spots to lay their eggs (moist soil being their favorite).

While I couldn’t find a formal study testing Vicks VapoRub on fungus gnats in houseplants, there is research showing that menthol, camphor, and eucalyptus oil can be effective insect repellents, especially when used in indoor environments. So, while the science isn’t exactly airtight, it’s not without logic.

At the very least, the strong smell could theoretically discourage adult gnats from visiting plants long enough to lay eggs. And if fewer eggs are laid, the population eventually drops.

What Happened When I Tried It

I rubbed Vicks on all the plant pots on my kitchen windowsill, and yes, the room did briefly smell like a chest infections clinic. The fungus gnats certainly did not vanish overnight, but over the following two weeks, I definitely noticed a reduction. Not a miraculous retreat, but clearer airspace and fewer gnats dotted over those sticky yellow traps (for reference, I use these slightly more attractive, shaped traps from Amazon).

I topped up the Vicks every few days and, importantly, I kept up with the usual best watering practices: letting the soil dry out slightly, bottom watering, and regularly refreshing sticky traps to monitor the situation. An alternative remedy like Vicks is never going to be enough on its own, but when used in combination with other solutions, it can help tip the balance.

Perhaps just as crucially, it was easy and relied on a product I already had in the bathroom cabinet. No mixing solutions or introducing more moisture into the soil.

If you need any more convincing to try it, my mother-in-law claims it has totally eliminated the problem in her home.

Could Vicks Work for Other Pests?

Naturally, I’m curious to know if Vicks can be used to deter other pests, too. In theory, the ingredients could also deter ants, mosquitoes, and possibly slugs. But while it might reduce pests entering the home, it is not water-resistant and will quickly break down when exposed to rain or watering. This raises the question of whether regularly applying petroleum-based products outdoors is something you should be doing (I’d argue no).

Indoors, however, where the air is still and scents linger longer, it makes more sense as a supplementary deterrent. I know come spring I’m going to be testing it out next on ant entry points.

My Verdict on Vicks

So, would I recommend Vicks VapoRub as a houseplant pest miracle cure? No. But would I totally dismiss my mother-in-law’s advice? Also no. Used sparingly alongside other measures, I do think this hack has some merit. I like that it’s low-effort and affordable. And if nothing else, it’s a reminder that sometimes old-fashioned gardening advice passed on anecdotally does have a place. I’ll never stop enjoying hearing about and trying out new hacks – and I’m grateful that my mother-in-law told me about this one (even if she did bring in the gnats in the first place!).