Do Flies Mean Your House Is Dirty?

About a month ago, it began. When I walked into my kitchen for my morning coffee, I noticed tiny invaders: little black flies crowded around my (empty! bleached!) sink.

Panicked, I started looking around for the usual suspects: old food, an opened packet, a grubby bin.

But I found nothing. Though they’re not overwhelming, the little visitors have survived deep clean after frantic deep clean.

Across the UK, house flies are swarming. So, what does it mean – and does their appearance always signify a dirty home? Professor Adam Hart, a professor and entomologist at the University of Gloucestershire, shared his expertise.

“House flies aren’t a reliable indicator that your home is dirty. They’re attracted by opportunities rather than making judgements about housekeeping,” Prof Hart explained.

The issue might not be in your home, but near it, he added.

“Open doors and windows, warm weather, and nearby breeding sites such as compost heaps, bins, animal waste or even neighbouring properties can all increase the number of flies that find their way indoors.”

That’s not to say they’re not tempted by the smells and items in your house, though: “Once inside, they’re drawn to food smells, sugary drinks, fruit, pet food and other organic material.”

Sometimes, Prof Hart said, a sudden influx of flies can signal an unaddressed issue. “If you’re suddenly seeing large numbers of flies, it’s worth checking for a specific source,” he said.

“An unnoticed food spill, overflowing bin, dead rodent in a wall cavity, or even a forgotten potato or onion at the back of a cupboard can provide an ideal breeding site.”

“They don’t breed indoors but often enter buildings in late summer and autumn to overwinter, sometimes appearing in surprisingly large numbers.”

Cluster flies can enter your home through tiny cracks in your walls or near your windowsills.

The best way to reduce flies, the entomologist said, is to remove what attracts them.

That involves the usual steps. “Keep food covered, empty bins regularly, clean up spills promptly and don’t leave pet food out longer than necessary. Good fly screens and keeping doors closed where possible will also reduce the number entering,” he advised.

But if you’re sure your house is clean, and flies seem to be sticking around regardless, “it may be worth looking outside the home for the source or considering whether there’s a hidden breeding site that needs attention”.

Those spots can include compost heaps and even your neighbour’s home or garden.

“Most flies are more of a nuisance than a health risk in the home, but because they can move between waste and food, they can carry bacteria mechanically on their feet and bodies,” Prof Hart ended.

“That’s another good reason to keep food preparation areas clean and deal with any persistent fly problem promptly.”