Green Is Not a Big Deal

One mystery I’ve never solved is why patients worry about green bodily fluids.

Guests with a cough tell me that they wouldn’t have called if their mucus hadn’t turned green. In fact, in an otherwise healthy person, green mucus is rarely a serious sign. Ditto for yellow. Everyone’s respiratory tract produces a quart of mucus a day. When it’s irritated, it produces more, and it can change color.

If you vomit on an empty stomach you might see bile which is green. This has no great significance. Many patients believe that they shouldn’t vomit if their stomach is empty, so something ominous is happening. This is not so. The signal to vomit comes from your brain, not your stomach.

Patients with diarrhea often save it in the toilet for my examination. I consider it bad manners to refuse to look, but normal stool can turn green.

There are exceptions. Blood from these orifices is never normal, so it’s OK to show me. If your stool or vomitus is black – pitch black, never dark brown – that’s usually bleeding.

A good rule (although my lawyer insists that I add that plenty of exceptions exist) is that you should see a doctor if you feel bad. If you don’t feel bad, it’s probably not necessary. Don’t pay too much attention to green stuff.