Why do I have so many flies in my house? 5 reasons and 5 ways to keep them out

Wondering why you have so many flies in the house? These are the key problems to watch out for, according to pest experts

A black fly sitting on an interior blind
(Image credit: GettyImages)

It's that part of the year when we are asking ourselves: 'Why do I have so many flies in my house?', and of course, in some instances the answer is logical. If you're leaving your windows open for longer (or even overnight) then you're creating a free passage for all insects who previously stayed beyond your four walls. 

However, if you're facing a distinctly notable surge in flies, the reason could go beyond your windows and doors being left open. And if you discover why you have so many flies inside, you can easily find ways to keep flies out of the house, hopefully solving the problem for good. Here's what the control experts suggest, for a fly-free home all summer long.

Why do I have so many flies in my house? 

According to Nancy Troyano, a Board Certified Entomologist and Director of Operations Education and Training for Ehrlich Pest Control, there are 5 reasons why you may have flies in your home. And, you can prevent them all easily.

1. Spilt food and beverages in your home

Bowl of fruit

(Image credit: Future/Emma Lee)

If you're wondering how to get rid of fruit flies as well as house flies, the solution could be as simple as cleaning any spilled food or drink in your home. 

'Fruit flies breed on moist, decaying organic matter, such as fruit or spilled beverages. If there is a place for these insects to breed, they will continue coming back,' Nancy warns. 

The expert adds that the reproduction rate of flies is also extremely high, as adult female flies can lay hundreds of eggs that develop into adults in as little as seven days. Therefore, it's important to keep food debris and liquid spillages cleaned up as soon as possible. 

2. Garbage near an open window 

Teal painted solid wood shutters

(Image credit: Paper & Paint Library)

As already suggested, one of the most common reasons why you have flies in your home is if you have your window or door open more than usual. However, NYC Pest Inspection Expert Diana Ludwiczak explains that the problem extends beyond the obvious entry point. 

'Check the perimeter of your home or apartment. Sometimes there is something attracting them close to your window or door on the outside, and they make their way in,' he says. This could be as simple as some garbage in the can near your window or some cracks in your drainpipe. 

'Some flies like drain flies can enter through hairline cracks in a drain pipe. Then they can begin laying eggs. It’s best to use an enzymatic drain cleaner a few times per year if you frequently get drain flies,' Craig adds. 

If your can sits within the vicinity of your window, it may be worthwhile investing in one of the best fly repellent plants that will deter the creatures when they arrive at your window.   

3. Scents from your pet

Pets in the heat

(Image credit: Future)

If you're living in a pet-friendly home, you will already know about the importance of cleaning up after your animal. However, if you're spotting an increase in flies, it may be worth giving your pet's litter tray an extra clean or putting uneaten food away. 

'Not only are feces perfect breeding places for flies, but they may also land there before landing on your food,' Nancy says. 

4. Standing water

Indoor plants in potting shed

(Image credit: Future)

If you've ever investigated how to get rid of gnats in plants, you may already know how much pests love water, and the common fly is no exception. 'Do not leave standing water anywhere in or around your home, including in watering cans and pot plants,' Nancy says. 

Craig Wilson, a horticulture expert, and Director of Gardener’s Dream Ltd similarly reinforces her warning. 'Overwatering plants creates an excessively moist environment, an environment that flies thrive in,' he says. He warns that overwatering may also cause stagnant pools of water which begin to harbor bacteria, flies also thrive where there is any bacteria.

5. Growing seasoning and spice

Kitchen wall decor ideas with blue half painted wall

(Image credit: Annie Sloan)

Just as Nancy warns that flies are attracted to the scent of food, Craig suggests that growing seasonings and spices may be the reason why you face a surge in pests in your home. 

'Those who grow their own spices may also be victims of a surplus of flies. Aromatic herbs like fennel and dill seem to attract the insects largely due to their fine-smelling scent,' he warns. 

So, if you're looking for the best houseplants for you, it may be worth remembering their appeal to flies in the process. 

Where are all the flies in my house coming from?

It's likely that the flies in your house are coming from a source near the house (typically your backyard) where there is rotting fruit and vegetables or garbage. So, if you have compost near the house, fruit lying on the ground or open garbage cans, it's time to do some housekeeping. The added benefits? Dealing with these will also help get rid of rats and deter raccoons.

Megan Slack
Head of Celebrity Style News

Megan is the Head of Celebrity Style News at Homes & Gardens. She first joined Future Plc as a News Writer across their interiors titles, including Livingetc and Real Homes, before becoming H&G's News Editor in April 2022. She now leads the Celebrity/ News team. Before joining Future, Megan worked as a News Explainer at The Telegraph, following her MA in International Journalism at the University of Leeds. During her BA in English Literature and Creative Writing, she gained writing experience in the US while studying in New York. Megan also focused on travel writing during her time living in Paris, where she produced content for a French travel site. She currently lives in London with her antique typewriter and an expansive collection of houseplants.