House flies are a common sight, often annoying as they buzz and land on us. Their persistent presence is not random; it is driven by a complex interplay of sensory cues and biological needs that draw them to humans.
What Draws Them Near
House flies possess keen senses that allow them to detect humans from a distance. They are particularly sensitive to volatile organic compounds (VOCs) emitted by human skin. These compounds, produced by bacteria interacting with sweat and skin oils, signal a potential source of moisture and nutrients.
Flies also detect the carbon dioxide (CO2) exhaled by humans, a strong indicator of a living organism. This CO2 plume helps flies locate hosts. Additionally, the warmth radiated by the human body serves as an attractant, especially in cooler environments. The moisture from sweat on human skin provides a readily available water source.
Why They Make Contact
Once attracted, flies land directly on skin for several reasons. House flies “taste” with their feet, using sensory receptors on their tarsi to explore surfaces for edible substances. They search for residual food particles, salts, sugars, or proteins present on the skin.
Flies may also land to regurgitate digestive fluids onto solid surfaces, including human skin. This process helps them dissolve solid food particles, making them easier to ingest.
Human skin provides a convenient perch for flies to rest or groom themselves, a behavior where they rub their legs together to clean their sensory organs.
Potential Health Concerns
House flies can act as vectors for various pathogens. They frequently visit unsanitary environments such as decaying organic matter, feces, and garbage, where they pick up bacteria, viruses, and parasites on their bodies and mouthparts.
Pathogen transmission occurs mechanically when a fly carries these microorganisms from a contaminated surface to a human or food. This can happen through direct contact when the fly lands, walks, or regurgitates on skin, or indirectly if it lands on food that is later consumed.
Flies transmit agents causing food poisoning, such as E. coli and Salmonella, along with other gastrointestinal issues. While a single landing’s risk is low, their potential to spread illness is significant, especially in poor sanitation environments.
Keeping Flies at Bay
Reducing the likelihood of house flies landing on you involves a multi-faceted approach, focusing on personal habits and environmental management. Maintaining good personal hygiene, including regular bathing and changing clothes, helps minimize attractive body odors and sweat.
Environmental cleanliness plays a significant role in deterring flies. Promptly cleaning up food spills and storing food in airtight containers eliminates their food sources. Regularly emptying and sealing trash cans prevents flies from breeding. Outdoors, removing standing water, pet waste, and managing compost piles can reduce local fly populations.
Exclusion methods are also effective in preventing flies from entering indoor spaces. Ensure windows and doors have well-maintained screens without tears or gaps. Sealing cracks and crevices around windows, doors, and vents can further block access points. Some insect repellents containing essential oils can also act as deterrents.