Citronellal does the heavy lifting.

Yes, the main active chemical in citronella that bugs hate is citronellal.

It’s a natural compound found in citronella oil (extracted from lemongrass-type plants like Cymbopogon nardus). Citronellal works by masking the scents that attract insects like mosquitoes, making it harder for them to find you. There are secondary compounds too—citronellol and geraniol—but citronellal is the star. That’s why most citronella candles and sprays list it as the active ingredient.

Worth noting: citronella is not super strong. It’s okay for a backyard hangout, but if you’re in mosquito-heavy territory, DEET or picaridin will run circles around it. Citronella evaporates quickly and loses effectiveness after about an hour.

Still, if you like the smell and don’t need heavy duty protection, it’s a fine choice. Just don’t expect miracles.