Can Onions Give You E. Coli? Here's What We Know

In October 2024, various news outlets reported an E. coli outbreak associated with McDonald's Quarter Pounders. Dozens of patrons of the fast food restaurant became sick after eating the contaminated burgers. (Sadly, at least one person died.) However, the suspected source of E. coli wasn't the meat that was used in the patties; it was the sliced onions sourced from a supplier called Taylor Farms, according to the updated alert from U.S. Centers for Disease Control and Prevention (CDC).

With this in mind, you may be wondering if you're putting yourself at risk every time you eat raw onions at home or in a restaurant. You'll be relieved to know that eating onions is generally safe, not to mention healthy. (Onions contain a surprising amount of valuable nutrients, including antioxidants, potassium, and vitamin C, according to Healthline.) With that said, you should always be cautious when handling, preparing, and consuming onions. Like all types of produce (particularly sprouts and vegetables, as noted by the World Health Organization), onions are susceptible to harboring E. coli that can be passed on to unsuspecting consumers.

Ironically, E. coli is by and large a normal and relatively harmless bacteria, as described by the Mayo Clinic. In fact, you probably have a strain of E. coli living in your gut right now, since it's commonly seen in the digestive tracts of humans and animals. There, it can be an asset to "good" stomach bacteria and assist in the creation of a beneficial gut biome (via the National Institute of Health).

When does E. coli become a problem? The short answer is when unwanted strains start to develop. This includes the strain known as E. coli O157:H7. This strain of E. coli comes from outside sources (not internal ones, like your intestines), including on vegetables, according to Johns Hopkins Medicine. Donald Schaffner, an expert from Rutgers University, told the CBC about a few ways that E. coli O157:H7 contamination could arise, such as agricultural producers using untreated manure, water that was contaminated, or unsafe production and storage methods.

Since the conditions must be ideal for unhealthy strains like E. coli O157:H7 to grow, most onions never become contaminated with the bacteria. But if contaminated onions are sold in grocery stores or sent to public restaurants for use in their menu items (as was the case in the McDonald's outbreak), they can create widespread health issues.

How do you know if you've been exposed to a type of E. coli that negatively affects your body? It typically takes a couple of days for people who've eaten foods tainted with E. coli to experience symptoms, but the symptoms are usually concentrated within the stomach and abdomen, according to the CDC.

For instance, classic E. coli poisoning side effects include vomiting, nausea, a low-grade fever, abdominal cramping, loose bowels (and sometimes bloody stools), and belly pain. Fortunately, most people's bodies can flush out E. coli toxins over a few days without medical intervention.

E. coli can become dangerous, though. Children, older individuals, and people who are immunocompromised are more likely to be hospitalized or die from E. coli food poisoning. Consequently, you should be doubly conscientious about practicing safe food hygiene and consumption measures if you or a loved one falls into one of those higher-risk demographics.

It's not practical to avoid all encounters with E. coli O157:H7 because the bacteria can't be seen, tasted, or smelled. Foods that contain E. coli O157:H7 may appear to be completely normal. But you can implement strategies to make it harder for toxic strains of E. coli to develop and spread.

A first line of defense against E. coli is to keep a clean kitchen. Sanitize your utensils and cutting boards, wipe up countertop spills, put food away in a timely manner, and perhaps most importantly, wash your hands. Taking small (but important) steps can have a big impact on whether or not E. coli appears in your home.

Secondly, eat or cook your onions as soon as you cut them. Food safety experts also warned against using pre-cut fresh vegetables that have been bagged since cutting increases contamination risk by exposing the food to airborne pathogens (via NBC News). Of course, if you suspect that any ingredients might not be safe, toss them out. Finally, stay in the know about food recalls and alerts. That way, you'll be less likely to unintentionally consume E. coli O157:H7.

What's the key takeaway? Most onions aren't contaminated with E. coli O157:H7 bacteria. Therefore, feel free to grab your soup cookbook and make a batch of French onion soup.