Watermelon frost, or Xigua Shuang, is prescribed in traditional Chinese medicine to relieve ulcers, sore throats, toothaches, minor burns and cuts. Its primary active ingredient is extracted from watermelon. First, a cavity is dug out, which is packed with mirabilite, also known as Glauber’s salt. The watermelon is then covered. After a few days, “frost” appears on the skin. Check out the video for more details.