Essential oils (like citronella) are just not that great at repelling mosquitoes and ticks. And in candle form, there's no indication that they provide more protection than any other candle ...

But there’s no indication that citronella candles provide more protection than any other smoke. Repellent bracelets, mosquito traps, and sound-based products likely won’t work, either.

When a citronella candle is lit, the heat from the flame causes the citronella oil to evaporate into the air. As the oil vapor disperses, it creates a fragrant barrier that confuses mosquitoes ...