I've never used white sugar for sunburns(seems messy) but it works wonders for other burns. Covering the burned area with white sugar will remove the heat in about 20 min. It also keeps the area from festering later. I've used it on burns from my iron, hot stove grease, fireplace burns, even 4th of July sparklers. Anything you can imagine. My daughter spilled boiling water on her foot & ankle. I filled a plastic grocery bag with enough sugar to cover the burned area. 20 min later the pain was gone. I missed a small place that was just above the bag line. That place festered and went thru the usual aftermath of a bad burn, while the part covered by the sugar remained healthy. This won't take away the blistering just the pain underneath it. You can tell when the sugar has worked by removing the sugar periodically and if it still hurts put more on again.