You've thrown up the contents of your stomach, but continue to retch. You're convinced there can't be anything left to vomit, yet here you are: hunched over the loo, expelling a bitter-tasting and filmy mucous.
What you're experiencing -- vomiting bile -- typically comes at the tail end of a major puke session. And most of the time, it's nothing to worry about. It's just the result of throwing up on an empty stomach.
Thick and sticky with a greenish-yellow hue, bile is produced by the liver, then secreted and stored in the gallbladder. The gallbladder meters out bile while you eat, releasing it in the duodenum -- the first and smallest segment of the small intestine -- to digest fat. Bile also helps eliminate bilirubin, a waste product of red blood cells [source: Merck].
If there's bile in your vomit, it's because bile from the small intestine has entered the stomach. Normally, the contents of the stomach travel through the pyloric valve, a ring-shaped muscle in the stomach, and into the small intestine where they mix with bile. The pyloric valve usually opens about one-eighth of an inch, releases an ounce (3.5 milliliters) of stomach contents, and then constricts to wall off the opening between the stomach and small intestine. However, there are instances when the pyloric valve does not fully close, allowing bile to flow upstream from the small intestine into the stomach.
This can happen during times of excessive vomiting, like when you catch a stomach "bug" (known as gastroenteritis) or get food poisoning. Sometimes, however, vomiting bile is the result of other maladies. Bile reflux, for example, is characterized by upper abdominal pain, frequent heartburn, a cough or hoarseness, weight loss and vomiting greenish-yellow bile. Bile reflux can also be a side effect of surgeries to the gallbladder or gastrointestinal tract or can be caused by peptic ulcers blocking the pyloric valve [source: Mayo Clinic].
Alcohol or food allergies can cause some people to vomit bile, too. Because of intolerance toward alcohol or certain foods, the body will ramp up bile production as it attempts to remove the toxin. In the case of food allergies, the vomiting follows breathing difficulties, stomach pains and reactions such as a runny nose.
In some instances, an intestinal blockage may be to blame. When the intestine becomes twisted, a blockage won't allow food to pass, resulting in severe pain, constipation and the vomiting of bile, which backs up into the stomach. Cyclic vomiting disorder (CVD) is another possibility, a rare condition of prolonged vomiting that can last for more than a month at a time. As the vomiting continues, a person suffering from CVD will begin to throw up bile [source: New Health Guide].
If you begin to throw up bile, check with your physician to see if your cluster of symptoms signals a relatively harmless, temporary condition -- or something more serious.