Vomiting could be a sign of a contagious "stomach bug." It may also be due to non-contagious factors that don’t require you to stay home, including pregnancy, food poisoning, or gallbladder disease. If you’re not sure why you’re throwing up, it’s best to stay home and watch for other symptoms or contact your doctor. Even if you’re not contagious, vomiting can make you weak and unable to effectively or safely work, so staying home when you’re able is the best choice.