Watermelon frost spray (powder) is an herbal product that has been popular in China for centuries to fight bad breath, sore throat and oral inflammation. Oct 15, Compound watermelon frost powder. In the 17th century during the Qing Dynasty , a famous doctor named Gu Shicheng recorded 'Sanjin. watermelonpoint.com: Sanjin Watermelon Frost Spray - Breath Freshener ( Oz.) - 1 If I apply this powder to the sore at the beginning, sometimes they won't even.