A 67-year-old woman is in critical condition after drinking toxic tea at a Dickey’s Barbecue Pit in South Jordan, Utah.

Jan Harding took a single sip of sweet tea and subsequently spit it out, telling her husband she thought she drank acid. In actuality, it was lye, an odorless, highly toxic chemical the restaurant uses to degrease deep fryers. Tom Richmond, a professor of chemistry at the University of Utah, told ABC News the chemical is also found in drain cleaners and could dissolve a person’s insides.

Harding sustained esophageal burns from the beverage, and ABC reported doctors are working to see if she also sustained tears to both her esophagus and stomach. The owner of the Dickey's Harding visited released a statement saying that he’s praying for Harding and won’t release the specifics out of respect for her and her family.

Though an isolated incident, the million dollar question is how something like this could happen. Investigators know so far that the chemical was in the food prep area when an employee mistook it for powdered sugar (lye is also available in liquid form). Dickey’s is still open, and there is no word on whether or not said employee still works there.

These are very particular circumstances, but consumers are more likely to consume toxic tea than they might think. A study conducted by EuroFins, an analytic testing company, found 91 percent of Celestial Seasonings teas contained illegal levels of pesticides.

Collective Evolution ran with the study and looked to see if any other teas frequently sold in-stores are contaminated, too. And of course there are. Tetley, Bigelow, Mighty Leaf, Teavana, Tazo, and David’s Tea were among the worst offenders.

Manufacturers get away with this by masking questionable ingredients as “natural additives” on their nutrition label, including Natural Red #4.

Practice Safe Tea

Again, investigators report this is an isolated incident. But generally speaking, too much sweet tea, whether it’s from a restaurant or grocery store, can increase your risk for kidney stones as a result of a naturally occurring chemical called high oxalate content, according to Dr. Lee Hammontree, of the Urology Centers of Alabama. It inhibits calcium absorption.

Fast food sweet tea nearly contains the same amount of calories and sugar as a regular 12-ounce soda. Unsweetened varieties would be the healthier option.

And when navigating store aisles, CE recommends options from  trustworthy companies such as Teatulia, Numi and Traditional Medicinals.