The practice of forbidding smoking, eating, and drinking in laboratories is one of the basic good hygiene practices. Unfortunately, it is often one of the most frequently disregarded. Too many people seem to have a "good reason" for continuing these bad habits. None of these reasons are good enough.
These practices protect people in laboratories from ingesting toxic chemicals or infectious materials. The stuff that's on your hands ends up in your mouth.
I've watched science department heads drink coffee while supervising the lab. I've seen teachers make stir-fried vegetables in a wok in the lab between classes for lunch. Don't do it. Set a good example yourself and enforce the rules.
Set up a separate area that can be used for taking breaks, making coffee, and consuming food. Don't allow it in the lab. And that includes applying cosmetics, too.
It’s not only a bad practice but it is also against the law. Two OSHA regulations speak specifically to this unfortunately widespread practice. One is the bloodborne pathogens standard, 29CFR1910.1030. The other is the sanitation standard, 29CFR1910.141(g)2/4.
There are many worthwhile experiments that involve eating something. For example, teaching colligative properties by making ice cream. Take your students to the cafeteria, use paper plates and plastic utensils and teach your students about safe practices at the same time. Remember, safety is a teachable moment.
Also remember, Pierce College in Tacoma, Washington was sued for 2.5 million dollars following the death of a young woman. She drank a saline solution as part of an A&P class. It contained sodium azide as a preservative. She died four days later.
Many laboratories have ice machines. They should be clearly labeled: “This Ice Is Not for Human Consumption”.
Source: Kaufman, James A., Laboratory Safety Guidelines - Expanded Edition, The Laboratory Safety Institute, www.labsafetyinstitute.org