It happens in a lot of cases, for instance where there's food poisoning the body will try to get rid of the (contaminated food/drink etc) by vomiting. It comes first in form of nausea which comes uncomfortable right before the food expulsion.
With vomiting there's a process, it starts with nausea and salivation then retching and the expulsion of food in the stomach through the mouth.
In common cases vomiting food poisoning/stomach bug etc which can be treated easily (with drugs usually to stop the reflex action) but in some cases, they may be a symptom of an underlying health issue which require urgent medical attention.
1. Vomiting after getting hit in the abdomen (or even the head) may indicate a sign of internal injury or concussion where expert help should be sought as fast as possible.
2. Vomiting immediately after waking up can be a sign of brain tumor and in some cases, they come with headache.
3. Vomiting colours like dark red may be as a result of ulcer and green as a result of bile which signifies a blockage of the digestive system.
4. Vomiting accompanied by pain in the stomach that is not diarrhea is usually a sign of appendicitis and in this case, fast help should be sought.