What Really Draws Flies to People and How to Keep Them Away

Few nuisances compare to a fly relentlessly buzzing near your face, evading every attempt to swat it. Whether it’s a common housefly circling your meal or a mosquito targeting your exposed skin, these small insects seem endlessly drawn to us. But what exactly attracts them to humans? And more importantly, what methods can help deter them?

The Attraction of Flies to Humans Explained

The specific reasons why flies seek out humans differ depending on their species; most are driven by instincts to locate nourishment, warmth, or suitable areas to deposit eggs. Some feed opportunistically, while others depend on blood meals as parasites.

“Certain types are attracted to us because we are warm-blooded mammals they can feed upon,” explains Jonathan Larson, an entomologist at the University of Kentucky. This includes species such as mosquitoes, deer flies, and horse flies, which detect humans by sensing carbon dioxide in our exhalations and other bodily scents.

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Humans Emit Scents Irresistible to Flies

Flies possess remarkable olfactory capabilities, able to identify food sources from great distances. Jody Gangloff-Kaufmann, an entomologist at Cornell University, notes that humans naturally release compounds like carbon dioxide, lactic acid, and carboxylic acid, which flies find especially attractive.

That said, not all people smell equally enticing to these insects. Sammy Ramsey, assistant professor of entomology at the University of Colorado Boulder, points out that individual variations in body chemistry, diet, and activity levels affect how appealing a person’s scent is to flies. “If smell were visible, you'd see an aura of aromas surrounding everyone you know,” he says. Some individuals simply draw more attention than others.

Why Houseflies Frequently Land on Skin

Unlike blood-feeding flies, houseflies (Musca domestica) don’t seek blood but are attracted to the nutrients found on skin. “Our skin hosts a variety of substances they can consume,” Larson explains. “Sweat and skin oils contain carbohydrates, proteins, and other compounds that flies can lap up like a convenience store’s snack selection.”

Nevertheless, sweat is not their primary food. Ramsey suggests that flies primarily lick our skin to replenish salts. When truly hungry, they will turn to decaying organic matter or human food. If they settle on your meal, they don’t just bite; they regurgitate digestive enzymes to liquefy it before sucking it up with their proboscis.

The Flies’ Sensory Systems for Finding Food and Avoiding Threats

Flies are expertly equipped to detect food and evade danger. Their antennae and body hairs house sensory receptors sensitive to airborne chemicals. Some species can trace odors over long distances, directing them straight to food sources.

After landing, a fly uses its feet, which contain taste receptors, to determine immediately if a surface is edible. This enables a rapid grab-and-go feeding strategy that helps them avoid being swatted.

Additionally, flies’ large, multi-faceted eyes provide nearly 360-degree vision. Their keen ability to spot even the slightest movement explains why they dodge swats so effectively.

Beyond Annoyance: Health Risks Associated with Houseflies

Houseflies aren’t just bothersome insects—they are also potential health hazards. Their habit of landing on various surfaces, including decaying organic matter and human food, makes them vectors for disease.

“They visit feces, contaminating their feet, and then they land on your food and regurgitate on it,” warns Larson. This behavior facilitates the spread of serious illnesses such as cholera, tuberculosis, and typhoid fever.

Effective Ways to Keep Flies at Bay

No single method repels all fly species, but several tactics can reduce their numbers and annoyance:

Wear protective clothing – Long sleeves and pants help prevent bites from blood-feeding flies.
Apply insect repellents – Formulations containing DEET or oil of lemon eucalyptus are effective against many flies.
Keep food sealed – Flies are drawn to exposed meals and leftovers.
Remove breeding sites – Eliminate standing water, garbage, and decaying debris to discourage flies from reproducing.

Remember, flies are simply following their biological drives. However, with some simple precautions, you can make yourself far less tempting to these persistent insects.

This article was originally published in livescience.