Gnats are tiny, winged insects, typically measuring between 1/16 and 1/8 of an inch. They are a common annoyance to humans, both indoors and outdoors. Understanding what attracts them to people and their surroundings offers insight into managing their impact. This article explores why gnats frequently bother humans and outlines practical approaches to minimize their presence.
Why Gnats are Drawn to Humans
Gnats possess highly developed senses that allow them to detect cues from humans, drawing them in. Carbon dioxide (CO2), which humans exhale, is a primary attractant. Gnats use the plume of CO2 to locate individuals, often congregating around faces where CO2 concentration is highest.
Human body odor and sweat also act as strong lures. Chemicals present in sweat, such as lactic acid and ammonia, along with compounds produced by skin bacteria, are highly appealing. The moisture and salt content found in sweat and tears further enhance this attraction. The warmth and humidity radiating from the human body mimic the warm, damp environments where gnats typically thrive. While chemical cues are primary, visual elements like movement and clothing color can also play a role in drawing gnats closer.
Different Ways Gnats Bother Us
Gnat species interact with humans differently. Non-biting gnats, such as fungus gnats and drain flies, do not feed on blood. Fungus gnats are often found swarming around indoor plants, attracted to the moisture and organic matter in soil. Drain flies are drawn to the decaying organic film in drains. Their annoyance stems primarily from their sheer presence and tendency to fly into faces, eyes, or drinks, seeking moisture and organic material.
Conversely, biting gnats, such as midges (“no-see-ums”), black flies, and sand flies, feed on blood. Female biting gnats require a blood meal for egg development, using specialized mouthparts to cut the skin and access blood. Their bites can result in itchy, red, and painful welts, often accompanied by localized swelling, caused by the body’s reaction to anticoagulants injected during feeding.
Common Gnat Habitats
Gnats primarily breed and thrive in environments rich in moisture and decaying organic matter. Indoors, fungus gnats frequently infest potted plants where soil remains consistently damp, feeding on fungi and plant roots. Drain flies, another common indoor nuisance, lay their eggs in the slimy organic film that accumulates within drains and other moist plumbing fixtures.
Outdoors, habitats vary depending on the gnat species. Black flies, for instance, lay their eggs and develop in clean, flowing water such as rivers and streams, often attaching to submerged objects. Biting midges are found in diverse semi-aquatic or aquatic habitats, including salt marshes, wet soil, mud, and decaying organic matter around water sources. Sand flies typically breed in humid habitats containing decaying organic material, such as animal burrows, tree holes, caves, and even cracks in soil. These outdoor breeding sites contribute to their abundance in human-occupied spaces.
Reducing Gnat Annoyance
Minimizing gnat annoyance involves targeting their attractants and breeding sites. Eliminating sources of standing water and excessive moisture is a primary step, both indoors and outdoors. This includes properly managing potted plant watering to allow soil to dry between waterings, cleaning drains regularly to remove organic buildup, and promptly addressing any leaky plumbing. Outdoors, clearing fallen fruit, grass clippings, and other decaying organic debris helps reduce breeding grounds.
Personal protection measures can also reduce encounters with gnats. Applying insect repellents containing active ingredients like DEET, picaridin, or oil of lemon eucalyptus can deter biting species. Wearing long sleeves, pants, and head nets can provide a physical barrier against bites. Environmental controls such as using fans, which disrupt their weak flight, and ensuring windows and doors have fine-mesh screens can help keep gnats out of indoor spaces. Adjusting outdoor lighting to use bug-light bulbs or low-voltage options can also reduce their attraction to illuminated areas at night.