The Gross Truth About Flies on Your Food — Should You Eat or Toss?

You're at a picnic, and just as you're about to take a bite, a pesky fly swoops down and lands on your food. Is it still safe to eat, or should you toss it out immediately? Many people believe that a brief fly landing is harmless, but the reality might surprise you.

What Happens When a Fly Lands on Food?

When a fly lands on your food, it's not just an annoyance — it can be a health risk. Flies are known to carry over 100 pathogens, including bacteria, viruses, and parasite eggs, which can stick to their bodies and legs after contact with contaminated surfaces like manure or rotting food. Because flies lack teeth, they release digestive enzymes onto food to break it down into a liquid form they can consume. The problem is that this vomit may carry pathogens from whatever the fly previously ate, posing a potential health risk. These germs can linger in the fly's saliva, increasing the risk of disease transmission each time it feeds. This process can leave behind germs or bacteria such as E. coli, Salmonella, Hepatitis A, and shigella, causing stomach pain, fever, and diarrhea.

How Quickly Food Can Be Contaminated

It only takes a second for a fly to contaminate your food, however, not all flies carry a disease. Most of the bacteria and viruses that flies can transmit are known as fecal pathogens, but they aren't present on everything a fly consumes. For these harmful microorganisms to reach your food, the fly must first come into contact with sources like feces or raw meat to pick them up. Once they land, these bacteria can transfer almost immediately. While a quick landing might not mean your food is entirely spoiled, the risk increases the longer the fly remains on the food.

While having flies around is always a worry, it's typically more problematic in rural areas. Flies are often more numerous there and are more likely to have been in contact with decaying animals or animal waste, increasing the potential for contamination.

When Should You Discard Food?

Outdoor barbecues and picnics are high-risk times for flies contaminating your food, as multiple fly landings increase the likelihood of germs being left behind. To minimize this risk, keep food covered when not eating, and consider discarding any that has been exposed to flies. The longer food is left uncovered, the greater the chance for harmful pathogens to spread. In other words, maybe skip the leftovers if there have been unwanted guests buzzing around your BBQ!

The Verdict

So, should you throw away food if a fly has landed on it? It depends. If it's just a brief landing, you might be safe. But if the fly lingered, or if the food has been sitting out for multiple candidates to land on, probably a good idea to throw it out!

References: Should I throw away food once a fly has landed on it? | What to do When a Fly Lands in Your Food