Anecdotal claims suggest that common kitchen spices, particularly cinnamon, offer a simple, non-toxic solution for controlling flying insects. This leads to a central question: do flies truly dislike the smell of cinnamon, and what is the scientific mechanism behind this effect? The answer lies in the spice’s powerful aromatic compounds and how they interact with an insect’s delicate sensory system.
The Chemical Basis of Cinnamon’s Repellent Effect
The strong aroma of cinnamon comes primarily from cinnamaldehyde, which makes up 60 to 80 percent of the essential oil’s composition. Cinnamaldehyde acts as a potent sensory irritant to many small insects, including various species of flies. Flies possess highly sensitive olfactory receptors used for navigation, finding food sources, and locating mates. When exposed to concentrated cinnamaldehyde vapors, these receptors become overwhelmed, disrupting the fly’s ability to process environmental cues. In high concentrations, the compound exhibits neurotoxic properties by interfering with the insect’s nervous system, which is documented to be toxic to house fly larvae and adult flies (e.g., a 10% oil solution).
Methods for Using Cinnamon as a Fly Repellent
One of the most practical methods for utilizing cinnamon’s repellent qualities is through an essential oil spray. A safe ratio involves mixing 10 to 15 drops of cinnamon essential oil with four ounces of water and a dispersing agent like witch hazel or vodka. This mixture should be shaken well before each use and lightly misted around doorways, window frames, and kitchen counters. For maximum potency, using essential oil derived from high-quality Cassia or Ceylon cinnamon is recommended.
Another simple technique is to use the spice in its whole or ground form near potential fly entry points. Diffusing the essential oil in an indoor space is also effective, as it disperses the cinnamaldehyde vapors throughout the air. Ground or whole cinnamon can be used in several ways:
- Placing cinnamon sticks in fruit bowls.
- Tucking sticks into sachets near trash cans to emit a continuous deterrent scent.
- Sprinkling a fine line of ground cinnamon across window sills.
- Lining the perimeter of a doorway to create a temporary barrier.
Effectiveness and Limitations of Cinnamon
Scientific evidence confirms that cinnamon can function as a deterrent, but its effectiveness depends on the specific application and environment. Studies show that a five percent cinnamon oil solution can strongly repel certain flies, like the horn fly. However, achieving this concentration in a home-use spray is challenging.
A primary limitation is the high volatility of the active compounds in cinnamon. The aromatic molecules evaporate quickly, meaning the repellent effect fades within just a few hours, especially in open or well-ventilated areas. This rapid dissipation necessitates frequent reapplication to maintain sustained deterrence. Cinnamon works best as a mild deterrent in small, enclosed spaces, such as temporarily keeping fruit flies away from a kitchen counter, and should not be viewed as a substitute for professional pest control or sanitation measures when dealing with a large infestation.