Small flies often buzz around humans, even when individuals feel clean. Their attraction stems from a complex interplay of biological cues and environmental factors. Understanding these reasons can help explain why these persistent pests seem so drawn to your personal space.
Identifying the Common Culprits
The small flies that frequently bother humans are often one of a few common types. Fruit flies (Drosophila melanogaster) are tiny, about 1/8 inch long, often with distinctive red eyes. They are strongly attracted to ripe, rotting, or fermenting fruits and vegetables, and other moist, sugary organic materials. You might find them hovering around kitchen counters, fruit bowls, or garbage disposals where food residues accumulate.
Fungus gnats are another frequent visitor, especially in homes with houseplants. These small, dark-bodied flies are slender with long legs and antennae, resembling miniature mosquitoes. They thrive in damp soil and feed on fungi and decaying plant matter, making overwatered potted plants an ideal breeding ground. While generally harmless to humans, they can be a nuisance, often flying near faces. Drain flies, also known as moth flies or sewer flies, are fuzzy, dark gray or black, with a moth-like appearance due to dense hairs on their bodies and wings. These flies are drawn to moist environments rich in decaying organic matter, such as the sludge found in sink drains, sewers, and stagnant water, and are not typically attracted to humans directly.
The Science of Attraction
Flies have sensitive sensory systems that detect cues from humans and their surroundings. A primary attractant is carbon dioxide (CO2), which humans exhale. Flies perceive CO2 as a signal indicating a potential host or suitable environment. Larger individuals or those engaged in physical activity exhale more CO2, potentially making them more noticeable.
Body odor and sweat also play a significant role in attracting various fly species. Human sweat contains compounds like lactic acid, ammonia, and certain fatty acids that appeal to many flies. These compounds, part of each person’s unique “scent signature,” are detected by the flies’ sensitive olfactory receptors. Warmth and moisture from the human body, particularly from sweat, further enhance this attraction, providing both a thermal cue and a source of hydration and salts.
Fruit flies, in particular, are drawn to volatile organic compounds (VOCs) released by ripening or fermenting foods. These scents can linger on skin or clothing, making individuals who have handled such items more attractive. Microbial communities on human skin also contribute to the overall scent profile, producing odors that draw flies seeking nutrients. Even “sweet” or “earthy” smells from personal care products or soil can inadvertently attract some species like fungus gnats.
Strategies to Deter Them
Reducing the attraction of these tiny flies involves a combination of personal hygiene and environmental management. Maintaining good personal hygiene, such as regular showering and wearing clean clothes, helps minimize the accumulation of sweat, body oils, and odors that attract flies. Some flies are drawn to the salts and nutrients on skin, so keeping skin clean can make you less appealing.
Environmental control is crucial, especially for types like fruit flies and drain flies. Promptly disposing of overripe produce, cleaning up food spills, and regularly emptying garbage cans with tight-fitting lids removes primary food and breeding sources for fruit flies. For drain flies, regularly cleaning drains with a stiff brush and hot water, or using bacterial gel cleaners, eliminates the organic film where they breed. Addressing any leaks or areas of stagnant water also reduces their preferred moist habitats.
Managing houseplants can help deter fungus gnats; avoid overwatering to keep soil dry, as these flies lay eggs in moist soil. Overall, keeping living spaces clean, dry, and free of decaying organic matter reduces the appeal of your home and person to these common small flies.