According to petMD, dogs often vomit for relatively benign reasons, usually in order to expel something from their stomachs or as a reaction to some form of gastric irritation. However, petMD cautions that prolonged vomiting is often symptomatic of a more serious underlying condition, such as gastrointestinal obstruction.
Vomiting is distinct from regurgitation, which is a spontaneous reaction that requires no abdominal effort from the dog and signaling problems occurring early in the digestive process. Dogs signal their intention to vomit by licking their lips, drooling and swallowing excessively, and will sometimes eat grass in order to induce vomiting. Global Animal notes that some dogs may naturally vomit everyday as a consequence of eating or drinking too quickly, snacking on grass or scavenging too many non-food items. Dogs also vomit due to the overproduction of stomach acid, a problem that can be addressed by feeding the dog more often and in smaller amounts.
The Chihuahua Rescue of Victoria warns that Chihuahuas in particular have sensitive stomachs and dietary needs. Owners of Chihuahua should resist the temptation to feed them table scraps, as sudden diet changes can cause an upset stomach and vomiting. Small portion sizes are also recommended because a Chihuahua's diminutive size makes large meals difficult to digest.