Kombucha is a sugary, black tea fermented by a flat, pancake-like symbiotic culture of bacteria and yeasts called the "Kombucha mushroom." It can be purchased at health food stores or made at home with the starter "mushroom," the beverage is "reputed" to boost immunity, cleanse the body, and produce other beneficial effects, but there is very little scientific evidence of these available in current literature.
Although the brew is mostly benign (it usually tastes very acidic, and contains traces of alcohol from the fermentation process), the American Cancer Society has warned that certain Kombucha starter cultures may contain contaminants such as molds and fungi, some of which can cause illness.
There have been reported cases of severe toxic reactions to Kombucha tea. In a recent report published in the Journal of Intensive Care Medicine by physicians at Cedars-Sinai Medical Center in Los Angeles, a 22-year-old male newly diagnosed with HIV became ill within twelve hours of consuming the tea. He was short of breath, his temperature spiked to 103.0 degrees Fahrenheit (39.4 Celsius), and he subsequently became combative and confused, requiring sedation and intubation for airway control. The Centers for Disease Control and Prevention pointed out that kombucha tea consumed in typical quantities approximately 4 ounces daily might not cause adverse effects in healthy persons. However, those with preexisting health problems or those who drink excessive quantities of the tea should beware.