Oh, summer—the season of warm sunny days, backyard BBQs, and… mosquitoes. Those pesky bloodsuckers seem to show up whenever we want to enjoy the great outdoors, totally crashing the party. The good news? There’s a non-toxic, eco-friendly, and surprisingly effective hack that will fight off those mini vampires for good: used coffee grounds.

By upcycling your used coffee grounds, you can both reduce waste and deter these unwelcome pests without resorting to harmful chemicals and sprays. Here’s everything you should know.

How Do Coffee Grounds Fight Off Mosquitoes?

While the smell of coffee might bring you joy in the morning, that’s not the case with mosquitoes. Mosquitoes hate strong smells. Just think about how much they can’t stand citronella candles. So it’s no surprise that the intense smell of coffee repulses them, quite literally making them fly off the other way.

While used coffee grounds are already pungent as-is, you can also burn them to up the odor even more. Whether that’s brewing the batch of coffee grounds for a second time or tossing them in a skillet to toast them, those mosquitoes won’t be a fan.

How to Use Coffee Grounds to Repel Mosquitoes

Ready to embrace your inner barista? Here’s how to upcycle your coffee grounds into a natural mosquito repellent. Just remember: If you have pets, avoid this tactic, as coffee grounds are toxic to dogs and cats if ingested.

1. Gather Your Grounds

Save the used coffee grounds from your daily coffee ritual. If you’re not a coffee drinker yourself, check with your local coffee shop—they’ll likely have some to spare.

2. Dry Them Out

Spread the grounds on a flat surface and let them dry. Don’t fret if they’re a little clumpy; just break them up with a fork or your hands.

3. Create a Barrier

Surround your patio, garden, or any other mosquito-prone area with a protective ring of coffee grounds. Think of it as an invisible moat guarding your personal space.

4. Keep Pets Away

If you have dogs or cats who may come into contact with the coffee grounds, either keep them away or avoid the method altogether, as ingesting them can be toxic.