It’s a truth universally acknowledged that teens love to vape. But vaping hasn’t been around for very long, so nobody knows how it will affect teen health in the long run. There’s building evidence that, while it’s safer to vape than it is to smoke cigarettes, the practice is addictive and can cause harm to the immune response of the respiratory system. On Thursday, a case study published in Pediatrics showed that vaping can have serious effects in the short term as well.

In the case study, physicians from the University of Pittsburgh Medical Center report that they recently received an 18-year-old patient who was experiencing extreme difficulties in breathing and stabbing chest pains. These symptoms, they write, emerged after she began vaping just three weeks earlier. After she was admitted to the hospital, she experienced respiratory failure and was diagnosed with hypersensitivity pneumonitis, also known as “wet lung.”

Her pediatrician and study lead Dr. Casey Sommerfeld says that it was the chemicals within the e-cigarette that caused lung damage and inflammation, which in turn triggered the majorly reactive immune response.

“It is difficult to speculate how frequently this could happen; however, there are a few case reports involving adults that developed respiratory distress following electronic cigarette use,” Sommerfeld told CNN on Thursday. “As electronic cigarette use increases, we will be seeing more case reports and side effects.”

E-cigarettes, vaping
Scientists are still learning about the long-term health effects of e-cigarettes.

Typically, hypersensitivity pneumonitis is a disease of the lungs that happens after an allergic reaction — usually triggered by a fungus, dust, molds, or chemicals — inflames the lungs. According to the American Lung Association “tiny air sacs in the lungs become inflamed as their walls fill with white blood cells, and, occasionally, the air sacs may also fill with fluid.”

Sommerfeld, who now works as a general pediatrician at Children’s Healthcare of Atlanta, says that her patient reacted in this way after her lungs reacted to chemicals in the e-cigarette. After the patient was treated with an I.V. drip of methylprednisolone, she left five days after admittance.

e-cigarettes, vaping
A graphic created by the CDC.

E-cigarettes, the tool you use to vape, produce an aerosol by heating a liquid that contains nicotine, flavorings, and other chemicals. According to the Centers for Disease Control and Prevention, these other chemicals can include ultra-fine particles that can be inhaled into the lungs; volatile organic compounds; heavy metals like nickel, tin, and lead; and cancer-causing chemicals. In January, scientists announced that vape juices that taste like cinnamon, popcorn, or vanilla contain chemicals that can cause tissue damage and inflammation.

“It’s difficult for consumers to know what e-cigarette products contain,” the CDC asserts. “For example, some e-cigarettes marketed as containing zero percent nicotine had been found to contain nicotine.”

It’s the flavoring chemicals in some e-cigarette liquids that some researchers are particularly concerned about. In 2016, Dr. Ilona Jaspers of the University of North Carolina School of Medicine presented research demonstrating that although these chemicals may be relatively safe for consumption, they are not necessarily safe to inhale. Doing so, some case studies show, can cause issues in the respiratory system.

In a commentary on this new study, Jaspers says that this case study highlights the potential for risk with e-cigarette use, which is extremely important to consider as vaping’s rise in popularity mounts. A 2016 report from the U.S. Surgeon General states that there was a 900 percent increase in e-cigarette use by high school students from 2011 to 2015.

“In addition to nicotine addiction, which by itself will have effects on the adolescent brain, we just do not know yet what the long term health effects of exposure to e-cigarettes may be,” Jaspers told CNN. Wet lung may be a rarity — and fear-mongering here isn’t the objective — but cases like this demonstrate that there’s a lot we don’t know about this very popular practice.