Doctors are warning that a viral technique for making a sweet treat in a flash could lead to serious consequences. Tanghulu is a common street food in Asia, where vendors skewer fruits like berries or grapes and dip them in a molten candy coating. TikTokers have seized on the treat’s mouthwatering colors and popularized a quick method involving the microwave .

They promise the signature glassy coating with only a couple of ingredients and in just five minutes, but doctors in multiple countries are speaking out to warn parents of an uptick in burns, some severe enough to require skin grafts . In order to reach the “hard crack” stage for that shiny coating, sugar must be heated to at least 300 F, much hotter than just boiling water. And, because it is sticky and viscous, it can result in prolonged skin contact that may make a scalding injury much more dangerous.

Surgeon Dr. Colleen Ryan of Boston hospital Shriners Children’s said in an Aug. 14 press release that they recently saw two patients with just this injury in the space of only two weeks, and that international word of mouth among doctors is reporting multiple cases of deep burns occurring with the technique shown on social media.

Australian food scientist and dietitian Ann Reardon of How to Cook That is sounding the alarm as well, in a YouTube video explaining the potential dangers of using an appliance that can only accommodate plastic or glass, for a recipe that should be made in a heatproof metal pan. As she .