Do Coffee Grounds Repel Mosquitoes? (Fast Facts)

We’ve all been bothered by mosquitoes in the yard, but will the smell of coffee repel them?

Mosquitoes hate the smell of coffee, so burning used, dried coffee grounds is a great way to repel them without killing them. Adding coffee grounds to still water in your yard also stops mosquitoes from laying their eggs in it, meaning no larvae will grow.

Let’s dive down into the topic of coffee grounds repelling mosquitoes in greater detail, and discover the exact steps of using them to keep the mozzies at bay when we’re out in the yard…

Do Coffee Grounds Repel Mosquitoes?

Do Mosquitoes Hate the Smell of Coffee?

Mosquitoes really don’t like the smell of coffee. In fact, they hate a lot of strong scents, and this is because they have such a powerful sense of smell.

Strong smells like coffee confuse mosquitoes. At the risk of grossing you out, mosquitoes find us humans by sniffing us out. To them, people give off a wonderfully enticing aroma of lactic acid and carbon dioxide.

A stronger smell, like coffee or the citronella in a tiki torch, blocks out our delicious scent.

So that’s why mosquitos hate certain smells: they can’t locate flesh to bite anymore. We know, it’s pretty disgusting. Burning smells make the best deterrents, and we’ll look at this in just a moment.

Can Coffee Grounds Kill Mosquitoes?

Coffee grounds won’t kill mosquitoes, although they may keep them at bay. The confusing aroma of coffee prevents mosquitoes from locating humans to snack on, but it won’t harm them.

However, it’s a different matter when it comes to eggs and larvae. It seems that if you add used coffee grounds to still water in your yard, the mosquitos won’t lay their eggs in it.

We’ve also heard that coffee grounds can kill mosquitos at the larvae stage, so it’s not too late to add coffee to standing water if the eggs have already been laid.

Please don’t add coffee to water that’s home to other creatures. This is because caffeine can affect the ammonia levels in water, ultimately harming wildlife such as fish.     

How Do I Use Coffee Grounds to Keep Mosquitoes Away? (Do I Burn Them?)

We’re sorry: simply sitting on your porch enjoying a cup of joe isn’t enough to keep the mosquitos away. While scattering bowls of used grounds around the patio may help a bit, for maximum effect, you really need to burn the coffee.

How do you make used coffee grounds into a smoking mozzie repellent? Follow these simple steps…

  • Don’t throw your used grounds on the compost or in the garbage. When you’ve finished brewing the coffee, rescue the used grounds and set them aside
  • Wet grounds won’t work, so take them out of the filter paper (if they’re in one) and scatter them across a large plate or tray to dry
  • Put them somewhere warm to dry out, like a sunny windowsill
  • You can speed up this process by putting them in a low-temperature oven or microwave
  • Transfer the dry grounds to a heat-proof container, like an old baking dish
  • Set it down in a good spot, preferably upwind 
  • Add a few drops of lighter fluid to the grounds to help them burn (not too many. You don’t want soaked grounds that go up in a flash)
  • Get kids and pets out of the way, just in case… Carefully light the coffee grounds
  • Want to make the smell extra horrible for the mosquitoes? Add things like cloves, bay leaves and eucalyptus leaves
  • If you prefer a slower smolder to a full-on smoke, cover the baking dish with a damp towel. The coffee mix should then smolder slowly through the damp fabric

If you fancy a more aesthetically pleasing way to burn coffee grounds, you can try mixing them with melted wax to create a coffee-scented candle.

It won’t be as potent as a tray full of smoldering grounds, but may be enough to pop on the bistro table on your balcony or porch. Here’s how to make simple coffee candles

It’s worth remembering that smoke works by masking human scent from the bugs. Those poor people out of the range of the smokey smell will continue to be mozzie magnets.

So, unless you plan to create a force field around your deck with lots of trays of burning grounds or dozens of coffee candles, it’s best to take a multi-repellent approach.

Other scents that mosquitoes don’t like include lavender, lemon balm, sage, and mint. As well as burning coffee grounds, you can help to create a natural anti-mosquito zone by planting these herbs in pots around your patio.

You can also spray a citronella-based repellent directly onto your skin, which means you’re protected wherever you are in the garden. Of course, prevention is a really important factor, so if you can, eliminate standing water from your yard.

How Do I Use Coffee Grounds to Keep Mosquitoes Away?

Are Coffee Grounds a General Bug Repellent? (Do They Repel Flies & Wasps?)

Caffeine is a natural bug repellent. This is actually why caffeine exists: the coffea plant has evolved to contain caffeine because it wants to keep insects away from its fruit. 

Coffee fact: this is why the Robusta bean has more caffeine than the Arabica bean. Robusta is grown in lower-altitude climates that have more bugs, so its shrubs have evolved to throw out more caffeine. Want more of a caffeine kick? Choose the bug-repelling Robusta!

Anyway, we digress. Your burning coffee may also keep other pests like flies and wasps away. At ground level, slugs and snails don’t care for it much either, so sprinkle a bit on the soil near your plants.

Caffeine may also repel cockroaches (although being roaches, they are probably as likely to eat the coffee grounds as they are to scurry away from them).

Are Mosquitoes Actually Attracted to Coffee?

Mosquitos aren’t attracted to coffee. It’s not a complicated love-hate relationship: it’s purely hate.

This is because the strong aroma of coffee (one of the things that attracts us humans to it!) repels the mosquito.

These bugs hunt by scent, and so powerful smells confuse its scent receptors. Something like burning coffee grounds or citronella smells stronger than we do, so the insects can no longer sniff us out.

We also know that caffeine is a natural bug repellent, so the combination of this strong chemical and the powerful scent is a definite turn-off for mozzies.

If you look at most popular mosquito repellents, the thing they have in common is that they all smell strongly. Mosquitoes hate garlic, lemon balm, mint, lavender, cider vinegar…

There are all sorts of everyday foods and items around your home and garden that will help to keep these pesky critters away from you.