The word “citronella” describes both a tropical tree and a fragrant grass, as well as the oil that is extracted from the grass. Citronella oil is very popular around the world as an “all natural” mosquito and tick repellant, and a number of sprays, candles, and other products feature it prominently. It isn’t normally as effective as commercial repellants, but a lot of this depends on the location and the individual; most clinical studies have shown that the insects are at least deterred by the scent, but whether they are deterred enough to leave the area is largely a matter of circumstance. In most cases neither the tree nor the grass has this same effect. The oil must be chemically extracted and used in high concentrations in order to get good results.
Two different plant varieties carry this name, and both are native to warm, tropical climates. The tree is known scientifically as Cardiopteridaceae. It’s native to Chile and other parts of South America, as well as Australia and some of the islands surrounding Fiji and Samoa. There are at least six related species in the family, and some are more shrub-like while others are fully branched trees. The leaves sometimes have a vague lemony scent, but they don’t typically contain much in the way of essential oils and aren’t normally consumed or used for any specific purpose.
A plant known commonly as lemongrass presents quite a different situation. It has many culinary uses, and is also the main source of citronella oil. Lemongrass is the common name for upwards of 45 different varieties of plant in the Cymbopogon family. Not all of these produce useful oil or have the same flavor profile. Most can be eaten, and grassy stalks are frequently used as an herb to add flavor and depth to any number of dishes. Those most common varieties in the fight against mosquitoes are Cymbopogon nardus and Cymbopogon winterianus, since these tend to have the highest concentration of oils in their leaves and shoots.
Simply planting a lemongrass shrub isn’t normally enough to deter mosquitoes, since the leaves and fronds themselves don’t usually have enough of a smell to challenge the insects’ territory. Some plants do have this capability, and some of them are sold under the “citronella” name for this reason — even though they aren’t usually related to the true plants in this family at all. The geranium often sold as Pelargonium “citrosum” is one of the most common examples. The quotation marks in the name indicate that the plant isn’t really in the citrosum family, but it acts like it does. People who plant this sort of low shrub around their patios or homes often find that the bugs stay away.
Getting the oil out of the grass usually requires a chemical process of distillation and extraction. The grasses are usually available somewhat regularly and the process isn’t difficult, which usually makes the oil fairly inexpensive to buy. There are a number of different preparations and concentrations, and the oil is commonly blended with other products or oils depending on how it’s intended to be used.
The oil appears perhaps most frequently in products designed to protect humans, pets, and open-air spaces from the public health risks posed by mosquitoes and ticks. A concerned person might spritz a bit of pure oil on their clothing, particularly on areas like shirt collars or pant legs where skin is first exposed, or he or she could use a oil-rich lotion or soap all over, typically before dressing. Innovative retailers have even created wristbands, personal wipes, and sunblock spray that contain the oil in varying concentrations. It’s is totally harmless to most people, although occasionally a mild irritation might develop from an allergic reaction.
Outside, people often use oil diffusers, room sprays, and candles that are rich with the oil. Candles are often particularly effective since mosquitoes, like most bugs, are also deterred by smoke. Consumers often have to pay attention when shopping, though, because merchants often call a candle or spray a deterrent even if it only contains very small concentrations of the essential oil. The more oil there is, the more effective the product is likely to be.
Insect Repellant Classification
Most of the insect repellants whose only active ingredient is the essential oil are not regulated by government agencies or oversight bodies because they are not technically pesticides. This can allow a great degree of variance when it comes to labeling and marketing, and can also impact things like quality control.
The smell of the oil is unpleasant to insects, but it doesn't harm or alter them in any way. A lotion with 10% concentration of the essential oil has been shown to deter insects for up to an hour. It isn’t usually as long lasting as most of the available chemical alternatives, though it is usually considered safer. It’s often combined with other natural insect repellants, such as catnip, cedar oil, mint, or rubbing alcohol to improve its effects.
Importance of Deterring Mosquitoes
Mosquitoes and ticks harbor many highly dangerous diseases, such as encephalitis, West Nile virus, and Lyme disease. The contagion passes into human and some animal bloodstreams since mosquito saliva acts as a carrier at the bite sight. Mosquito populations are best controlled by preventative measures such as eliminating breeding locations, but seasonal spikes in population an exposure at times when the insects are most active, particularly at dawn and dusk, make humans especially susceptible to bites. Any repellant measures are usually better than none, and the oils work well for many people.