Tea and herbal brews contain unlabeled and surprising ingredients in them, according to a study by three New York City high school students under the supervision of staff at Rockefeller University. The study is published in Scientific Reports.

It found that tea and herbal brews contained ingredients like annual bluegrass, chamomile, red bartsia (a garden flower), lantana (an ornamental tree), alfalfa, lemon balm, blackberry, and papaya.

For example, an herbal tea claiming to be made from “ginger root, linden, lemon peel, blackberry leaves, and lemongrass” contained annual bluegrass (a plant unrelated to lemongrass).

The study said these unlisted ingredients are largely harmless, except when they trigger acute allergies in a minority of consumers.

The tea and herbal brews also contained legitimate tea and herbal ingredients that for some reason weren’t listed on the packaging.

The students used DNA barcoding, which is described as a technology that “identifies and distinguishes known and unknown species quickly, cheaply, easily and accurately based on a snippet of genetic code.” Currently, scientists are building a library of DNA barcodes for known plants and animals.

The study examined 70 tea products and 60 herbal products from 33 manufactures in 17 countries.  They were purchased at 25 locations in New York City.

“After water, tea and its many herbal variations represent the world's most popular beverage -- by far. Literally billions of cups are consumed every day, more than all the coffee, pop and every other drink combined,” said Catherine Gamble, one of the high school student participants of the study.

“What's in those little bags of tea and herbal tea products is a matter of interest to billions of people,” she said.