What Causes Gnats in My House?

Bugs are never welcome in the house, but if you have small flies buzzing through your kitchen, bathroom or other rooms, they can be a particular nuisance. Commonly called gnats, these insects may be several different types of fly: fungus gnats, fruit flies or drain flies. The location of the flies usually helps you identify which one you're dealing with, but it helps to know what they look like and what they're attracted to in your home so you can get rid of them as quickly as possible.

Fungus Gnats

Fungus gnats are small, dark flies that typically appear in the house during fall and winter months. Their long legs and antennae give them a mosquito-like appearance, but they don't bite. They usually are near windows or other spots where houseplants are kept. That's because the larvae of fungus gnats feed on fungi, algae and other decaying material found in potted plants, and emerge as adults in approximately a week. In particular, they're drawn to extremely moist potting mixes, so they often appear if you tend to overwater your plants. Ensuring the top 1- to 2-inches of the soil are dry before watering again can help eliminate fungus gnats from your home.

Fruit Flies

If you spot extremely small, light brown flies in your kitchen, they likely are fruit flies. You often can distinguish them from other flies by their red eyes. As the name implies, fruit flies are attracted to ripened or rotting fruit and vegetables. Produce such as melons, grapes and tomatoes are likely culprits to draw these pests to your home. Onions, potatoes, bananas and other non-refrigerated produce from the grocery store also are favorites of fruit flies. Typically, these pests appear in larger numbers during late summer and early fall because they tend to infest newly harvested fruit and vegetables. They lay eggs on the surface of fermenting fruit or other organic materials, which they feed on. Keep produce in the refrigerator and get rid of overly ripe fruits and vegetables as soon as possible.

Sewer Flies

Gnats in the bathroom or around your kitchen sink probably are sewer or drain flies. They are fuzzy and dark in color so they have a moth-like appearance. However, they resemble fruit flies; you usually tell the two apart because sewer flies don't have red eyes. They are drawn to bacteria, sewage and other organic materials that commonly line drains, and often appear if there is a leaking or broken pipe. You may find them in a kitchen sink with an overflowing garbage disposal or around a seldom-used toilet. To keep your home free of sewer flies, regularly clean drain pipes, drain traps and toilets to remove gelatinous organic material that might collect in those areas to eliminate their food source.