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Dishwashers are powerful cleaning tools, but they may not eliminate foodborne pathogens on your dishes, glasses, and flatware.

Kimberly Holland
November 28, 2018
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Your dishwasher can perform a lot of magic. Put in a pie pan with baked-on blackberry cobbler, and in less than an hour, it comes out sparkling and clean. Your dishwasher can easily tackle that film of three-day-old macaroni and cheese, and it makes quick work of the crusted tomato soup at the bottom of your bowls.

But beyond getting food off your dishes, your dishwasher may not be getting rid of much else—bacteria, specifically.

Watch: 5 Uses for Vinegar in Your Kitchen

It’s difficult to pinpoint the temperature at which hot water will destroy bacteria and foodborne pathogens like what you encounter in a typical home kitchen environment. When cooking, you aim to reach internal temperatures of 140°F to 175°F for most foods. That is the range in which most harmful bacteria is killed off. Wouldn’t you then just aim to have water that hot in your dishwasher?

Yes, but it’s not certain how long the water has to be at that temperature to have a sanitizing effect, and it’s also difficult to know how hot the water inside your dishwasher gets.

The U.S. Food and Drug Administration (FDA) requires that commercial washers (the kind in restaurants) top 165°F in order to sanitize. Anything below 110°F, the FDA says, is too cold to ensure the water can even properly clean organic matter (read: food) from a surface, dish, or pan.

Today’s dishwashers likely get to 120°F at a minimum because that’s the standard setting on most home hot-water heaters. Dishwasher manufacturers can then heat the water to higher temps. The smartest bet, and what most dishwasher manufacturers aim for, is 145°F. Indeed, most dishwashers made today run between 130° and 170°F.

Some have even gone so far as to reach standards for sanitization set out by the National Sanitation Foundation (NSF). The NSF/ANSI Standard 184 says a dishwasher can claim it has a sanitizing cycle if a final extended hot-water rinse reaches 150°F. That means the machine kills 99.999 percent of bacteria.

This Bosch Ascenta Series Front Control Tall Tub Dishwasher is certified by the NSF for this sanitization capability, as is this LG Studio Black Stainless Steel Hidden SmoothTouch Control Dishwasher with Flexible Third Rack. If your machine doesn’t have the NSF certification, it either doesn’t have a sanitizing cycle, or that cycle isn’t hot enough to do what it promises.

Even if your dishwasher doesn’t get hot enough to sanitize your dishes, the hot water is handy for cleaning. High-temp water (even if it’s only 120°F), combined with soap, can attack oil, grime, grease, and stuck-on food to get your dishes sparkling clean. That leaves fewer food remnants and less film where more bacteria could live, linger, and grow.

If you’re worried your dishwasher isn’t hot enough, consider this: it’s probably fine, even if it doesn’t reach the sanitization threshold. You’re more likely to fall ill from foodborne pathogens in the food you eat (including undercooked food) or from cross-contamination on surfaces in your kitchen. The bacteria that might linger on your dishes is less likely to make you ill.

Plus, a dishwasher is certain to be hotter, in almost every case, than the hot water used in hand-washing. Most people cannot tolerate temps above 104°F, and that’s still not hot enough to kill some of the most potent foodborne germs, like E. coli and salmonella.

Your dishes are likely sanitized if you have a machine that washes hot enough, or they’re at least clean enough to limit bacterial growth even if they can’t get that high. So, go breathe a sigh of relief. Then get those dirty dishes out of your sink.

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