A lemon slice floating in a restaurant water glass may seem like a harmless way to add flavor, but it can sometimes raise questions about food hygiene. Lemons, like other foods, can pick up bacteria if they are handled improperly or stored under unsanitary conditions.

Research has found that lemon garnishes served in restaurants can sometimes carry microorganisms. A frequently cited study published in the Journal of Environmental Health examined lemon slices from restaurant drinks and found microbial contamination on some of the samples. However, finding bacteria on a food item does not automatically mean that it will make someone sick.

The potential problem comes from how the fruit is handled. Lemons may be touched during preparation, cutting, storage, and serving. If employees do not follow proper hand-washing and food-safety practices, bacteria can potentially be transferred to the fruit. The same basic concern applies to many other foods and garnishes served in restaurants.

That doesn’t mean you need to panic every time you see a lemon in your water. Restaurants are expected to follow food-safety rules, and most properly handled food is unlikely to cause illness. Still, if you are uncomfortable with a garnish or have a weakened immune system, asking for your drink without it is a simple precaution.

If you enjoy lemon water, washing fresh lemons before cutting them and using clean utensils at home can reduce the chance of contamination. The important lesson isn’t that every restaurant lemon is dangerous, but that food hygiene matters—even when something as ordinary as a small slice of fruit is involved.