Teens are getting high on an emerging drug called "fake weed," a concoction also known as K2 and "spice" that is also causing hallucinations, vomiting, agitation and other dangerous effects.

In the last month, Dr. Anthony Scalzo, a professor of toxicology at Saint Louis University, has seen nearly 30 cases of teenagers experiencing these adverse effects after smoking the fake weed, a legal substance that reportedly offers a marijuana-like high.

"K2 use is not limited to the Midwest; reports of its use are cropping up all over the country," Scalzo said. "I think K2 is likely a bigger problem than we're aware of at this time." For instance, Atlanta has seen about 12 cases recently.