If you ate a rotten egg, you should immediately wash it down with water and call a doctor. Eating a rotten egg can cause food poisoning, which is a serious condition. Food poisoning is a result of eating contaminated food, which can be caused by a number of factors. If you think you've eaten a rotten egg, the best course of action is to flush down the egg with water as quickly as possible. If you don't have any water nearby, you can try to induce vomiting. If that doesn't work, you should go to the hospital. Food poisoning can cause a number of serious symptoms, including diarrhea, vomiting, and fever.