What is nausea?
Nausea is the feeling of sickness and is often a precursor to actual vomiting (emesis) although not all cats who are nauseous do go on to vomit. Prolonged vomiting can be extremely debilitating to cats.
The purpose of nausea is to act as a warning as well as being protective. For example, nausea at a particularly unpleasant smell is going to put the cat off eating it and possibly save it ingesting something dangerous. Nausea accompanied by vomiting after ingesting a food or substance is usually to rid the body of a toxin. Such as food which has gone off or an ingested toxin. It also serves as a warning system of organ dysfunction or damage.