Can Drain Flies Bite?
No, drain flies (also known as moth flies or sink flies) do not bite people or pets. Their mouthparts are not designed for piercing skin or feeding on blood. Instead, these flies feed on organic matter and decaying debris found in drains, sewage systems, and other moist areas where bacteria and fungi thrive.
Do Drain Flies Bite?
People are most likely to mistakenly believe that drain flies have bitten them when they experience unexplained skin irritation or small red bumps that coincide with seeing the flies around sinks, tubs, or drains. In these situations, the timing and location can create a false connection between the two. Here are the most common scenarios:
Presence of flies near the irritated area: When drain flies are hovering in bathrooms or kitchens and someone notices bites or rashes nearby, it’s natural to assume the insects are responsible. In reality, the irritation often comes from another source—such as mosquitoes, fleas, bed bugs, or even contact dermatitis from soaps or cleaning agents.
Skin reactions from bacteria or fungi in drains: The organic slime where drain flies breed harbors bacteria and mold. When people clean drains without gloves, they can develop mild skin infections or allergic reactions that resemble bug bites. This leads many to think they were bitten by the flies rather than reacting to microbes.
Coincidental insect bites: If other biting pests (like gnats or no-see-ums) are active at the same time, their bites may be wrongly blamed on the more visible drain flies found indoors.
Allergic or psychosomatic responses: For individuals who are particularly sensitive to insect infestations, simply seeing small flies can cause itching or sensations known as formication (the feeling of bugs crawling on the skin), leading them to misattribute those sensations to bites.
In short, drain flies never bite, but their presence often coincides with environmental or health conditions that can mimic bite symptoms, making them an easy scapegoat.
Drain Fly Bites
Although drain flies cannot actually bite, reports of so-called “drain fly bites” usually stem from secondary issues linked to the conditions that allow these flies to thrive. The main risks are indirect rather than from the flies themselves:
Skin irritation or allergic reactions: Drain fly infestations often indicate buildup of organic sludge in drains—an environment rich in bacteria, mold, and fungi. When people come into contact with this material (for example, while cleaning a drain without protection), they can develop dermatitis, mild infections, or allergic rashes that may resemble insect bites. These reactions are caused by microbes or allergens, not by the flies.
Respiratory irritation: In heavy infestations, the fine hairs and debris shed from adult drain flies can become airborne. Prolonged exposure may trigger asthma-like symptoms or allergic responses, especially in people with respiratory sensitivities or weakened immune systems.
Psychological stress and misdiagnosis: Persistent swarms of small flies indoors can cause anxiety, itching sensations, or “phantom bite” complaints, leading individuals to misinterpret harmless contact with the insects as biting behavior. This can contribute to unnecessary worry or even dermatological conditions like delusional parasitosis.
Potential for contamination: While drain flies themselves are not known disease vectors, their larvae and adults can mechanically transfer bacteria from drains to surfaces when they crawl or rest, posing a minor sanitation concern in kitchens, bathrooms, or hospitals.
There are no medical risks from actual drain fly bites, but infestations can cause secondary skin, respiratory, and hygiene-related issues.
What Do Drain Fly Bites Look Like?
Because drain flies cannot bite, there are no true drain fly bites. However, people who believe they’ve been bitten often report skin symptoms that resemble mild insect bites—though these marks are caused by other factors:
Appearance of the marks:
Small, red, itchy bumps similar to mosquito or flea bites.
Sometimes slightly raised or clustered around exposed areas (like legs, arms, or ankles).
In some cases, a faint rash or irritation without distinct puncture marks.
Likely causes:
Contact irritation from cleaning drains, especially when exposed to bacteria, fungi, or harsh cleaning agents.
Real bites from other insects present in the same environment—such as midges, or no-see-ums—which are often mistaken for drain flies due to their size and behavior.
Allergic reactions to airborne particles from decaying organic matter or the flies themselves, especially in large infestations.
Distinguishing features:
True biting insects (like fleas or mosquitoes) leave a central puncture mark and typically bite in patterns or lines. “Drain fly bites,” on the other hand, lack any puncture wound and do not follow a pattern, indicating a non-insect cause.
If you notice “bites” while seeing drain flies around, the irritation almost certainly stems from another pest or environmental irritant, not the flies themselves.
What To Do About Drain Fly Bites
If you think you’ve been bitten by drain flies, the good news is that they cannot bite or sting, so the irritation is coming from another source—either another insect or a mild skin reaction unrelated to the flies. Here’s what you should do:
Treat the skin irritation:
Clean the affected area gently with soap and warm water to reduce the risk of infection.
Apply a cold compress to ease itching and swelling.
Use an over-the-counter hydrocortisone cream or antihistamine lotion to calm redness or itchiness.
Avoid scratching, since that can lead to secondary infection or worsen inflammation.
Identify the real cause:
Inspect the area for other biting insects such as no-see-ums, fleas, or mosquitoes that might be active indoors.
If irritation appeared after cleaning a drain or sink, the reaction may stem from contact with bacteria, mold, or cleaning chemicals, not insect activity.
Persistent or worsening symptoms should be checked by a healthcare provider, especially if you notice signs of infection (increasing redness, warmth, or pus).
Eliminate drain flies at the source:
Clean drains thoroughly using a stiff brush and an enzyme-based drain cleaner to break down organic buildup.
Pour boiling water down the drain daily for several days to flush out larvae.
Keep drains dry when possible and repair leaks to prevent the moist environments where drain flies breed.
In cases of large infestations, consider our professional pest control to ensure all breeding sites are eliminated. Contact us to learn more about our professional pest control services.
Treat the irritation as you would any mild skin reaction, then focus on sanitation and pest identification—since the real culprit is almost never the drain fly itself.