In most cases, green saliva is not actually saliva at all, but stomach bile, vomit, or other digestive enzymes. Sometimes saliva will become colored when one eats certain foods, such as lime-flavored snacks or certain vegetables. This is temporary and is not the sign of a health condition. At other times, someone may confuse mucus from the nasal cavities or lungs for green saliva. When mucus is dark like this, it usually signals an infection.
Occasionally, the appearance of greenish saliva is caused by stomach bile or vomit rising into the throat and mouth. This can be caused by acid reflux disorders, digestive upset, and other gastrointestinal problems. If it is an occasional issue, green bile may not automatically mean there is a problem. If it continues, or is accompanied by other symptoms like vomiting or abdominal pain, it should be investigated by a doctor.
Many times people mistake mucus for green saliva. This is perhaps the most common reason for green fluid being in the mouth, since mucus can come from both the nasal passages and the lungs. When infection is present, mucus will usually be yellow or greenish in color, and it may have a slight odor. It's also often thick, but this will vary. If mucus is coming from the nasal passages, it usually means the person is suffering from a sinus infection or cold. Lung infections are more serious, and are usually accompanied by coughing, trouble breathing, wheezing, and other symptoms.
An infection usually needs to be treated by a doctor, especially one found in the lungs. Sinus infections often clear up on their own. Lung infections may worsen and lead to serious complications. Anyone who notices a substance resembling green saliva upon coughing or wheezing should consult with a physician right away for further investigation.
Green saliva can also appear if one eats something that temporarily dyes the saliva an odd color. For instance, eating green-colored candy or dark green vegetables can cause the saliva to appear green. This is temporary and will clear up within several minutes to an hour or so, depending on the quantity eaten and how dark the saliva has become.
Those who are suffering from any severe or unusual symptoms should consult a doctor. If saliva appears to be an odd color without any known cause, this should be checked right away. In some cases, saliva may also be thicker than usual.