Surfactants in soap, by nature, leave a residue if not properly washed away. Dish soap alone would not leave enough residue to be dangerous. To be sure, a bottle of dish soap may be consumed. You'd probably puke and be rather uncomfortable, but it wouldn't hurt you. However, if you also drink liquid bleach or eat any other contaminated product, then you could suffer some serious health problems. The surfactant residue left behind by dish soap is toxic if ingested or come into contact with the skin. If you're eating food that has been in contact with the residue, such as when you clean dishes with it, you're going to want to try and wash it away before consuming the food. This can be done by soaking the affected items in a mixture of water and vinegar for several hours or using a commercial cleaner. Soap residues are known to cause irritation to the stomach and intestines if they are not removed before eating the contaminated food. This can lead to nausea, vomiting, and diarrhea. There have even been reports of people being hospitalized due to these reactions. It's important to keep in mind that just because something isn't fatal doesn't mean it isn't harmful. Dish soap residue is certainly no laughing matter! It's best to avoid contamination in the first place by following proper cleaning protocols when cooking for one person only.