There’s nothing more annoying than the persistent buzz of a fly indoors, not to mention the fact that some flies can transmit pathogens that cause serious illnesses such as food poisoning, cholera, and dysentery. Bottom line: Flies are never a good thing inside our homes.

Fortunately, out of the more than 110,000 species of flies, only a few types are common pests around the house. “The ones that cause the most problems are called filth flies. But they’re doing what they were born to do, which is to break down organic matter,” says Faith M. Oi, Ph.D., extension associate professor of urban entomology at the University of Florida. “If we can be mindful about our behaviors, we can minimize our chances of getting sick.”

Keeping them out of our homes in the first place is the goal. “The truth is there’s no silver bullet with fly control,” says Elmer Gray, entomologist and researcher with the University of Georgia. “But we can take some basic steps to limit their access to our homes.”  

Read on to learn how to keep flies away, including the best natural ways to keep flies out of your house.

Any type of fly can make its way indoors, including fruit flies and bottle flies, but the most common is house flies. You'll be able to determine the type by their size and where they're hanging out.

House flies are about 1/4 inch long with four dark stripes down their middles. They lay eggs in organic matter in places such as garbage, compost, or in the thin film inside recycling bins.

In ideal conditions, flies reproduce in less than a week, says Oi. The warmer the environment, the faster they progress through the life cycle from egg to adult fly. For example, if you forget to take out the trash, and then go on vacation for a week, you could have fly larvae wiggling around in your kitchen when you return.

Blow flies and bottle flies are other types of flies that sneak indoors. They are about the same size as house flies but have a metallic green, blue, or bronze sheen to their plump bodies. They breed in animal waste and carcasses. If you’re seeing these flies in large numbers indoors, you may have a dead animal, such as a bird or squirrel, in places such as the attic or chimney, says Gray.

Little filth flies such as drain flies breed in sludge and decaying matter that can build up in drain pipes, says Oi. They resemble tiny moths and are about 1/16 inch long with yellow to brown-black hairy bodies and wings they hold over their bodies when resting. You’ll see them in the kitchen near drains and garbage disposals.

Tiny fruit flies come in from outside, attracted to ripening produce on your kitchen counter, or they may be brought in on infested fruit. They’re about 1/8 inch long and have red eyes. They lay eggs on the surface of fermenting produce or in trash cans, drains, or recycling bins.

Common flies that get in your house do not bite, but some flies do, such as horse flies and black flies, which can be painful. Flies do spread germs that cause diseases like dysentery, typhoid fever, tuberculosis, food poisoning, and cholera. Because of this, discard any food flies have come in contact with.

Flies live up to nearly 30 days and quickly multiply since they can lay many eggs during that time. Depending on what type you’re dealing with, your approach to controlling flies may differ. But these tips will help keep flies away overall:

Make sure window screens are in good repair. “These are your first defense against flies,” says Gray. Screens with holes and gaps provide easy access for flies and other pests to enter.

Discard rotting produce, and don’t leave food waste like banana peels on your counter, says Oi. Make sure to take out indoor trash bags at least once a week to prevent rotting food from attracting flies into your home.

Outdoors, Gray recommends that you tie trash bags up and seal tightly inside the garbage can to retain odors, and keep the can far away from entrances to your house. Place compost bins as far away from the house as possible, says Oi.

You should also clean up pet waste every day, says Gray.

Besides keeping trash and recycling bins away from the house, you should also clean them regularly. Flies are attracted to fermentation, such as in alcoholic beverage cans, so rinse cans and food containers before tossing into the bin, says Oi.

When eating or cooking outdoors, it's important to protect your food. Cover picnic foods with fine mesh food covers, says Gray. Flies carry pathogens on their bodies, but they also defecate and regurgitate while walking around on food. That's unappetizing.

Run a box fan if you’re sitting or dining outdoors. Flies don’t like fast-moving air. “Enough air movement to be considered a ‘bad hair day’ keeps them away,” says Oi.

Flies are attracted to the gunk building up in your drain. Make sure to clean them regularly and if you see buildup, use a long brush to give it a thorough cleaning.

If you see flies and aren't sure where they are coming from or are just unsure if you have a problem, there are ways to tell. If you see an increase of flies in your home, swarms of flies outdoors, droppings, or maggots, you may have an infestation and need to call a professional.

If you’re not sure if you have drain flies, take a clear container, smear some petroleum jelly on it, and turn it upside down over the drain overnight. Drain flies will attempt to fly out and get stuck, says Oi. If you have drain flies, use a stiff drain brush and a drain cleaner to clear out sludge.

Despite what you’ve heard, DIY “repellants” don’t keep flies away. That goes for bars of pungent soap, essential oils, sonic repellant devices, and hanging up pennies in bags of water, a favorite Internet myth. “None of these theories are supported by science,” says Gray.

In addition, spraying insecticides to kill flies isn’t a good option. “Flies are resistant to most of the pesticides registered for their management,” says Oi. “And pesticides aren’t permanent. If you have a major infestation, you must find the source. They’re breeding somewhere.” You’ll need to contact a professional pest control company for assistance.

The best way to keep flies away outdoors is to get rid of their food and breeding sources. Flies don't like citronella and other strong scents like lavender, rosemary, catnip, and basil. A few plantings outdoors may help deter them. White outdoor lights may also attract flies, so switch to yellow bulbs. You should also remove any stagnant water or moisture sources where they may breed.

As for how to kill flies that make it indoors? Both Oi and Gray say the use of good, old-fashioned fly swatters is best. “It’s an effective, pesticide-free way to kill them,” says Gray.

Oi also suggests keeping sanitizing wipes handy to wipe down the swatter and the surface where the fly was smashed.

To keep them from being a problem indoors in the first place, hang sticky traps in the garage near entrances to your home. They’re not pleasant to look at but may help reduce the numbers that try to head inside when you open interior doors, says Gray.