Dilute standard white vinegar (5 percent acetic acid) in a 1-to-1 ratio with pure water, wet a cloth in the mixture then apply directly to sunburned areas.
Alternatively, spritz the mixture using a spray bottle with a mister setting. Use caution if there are any cuts or open blisters—vinegar STINGS!
Leave the vinegar on for 10 to 15 minutes and then feel free to wash it off to avoid the vinegar smell.
Apply full-strength, regular yellow mustard for the same benefits as the vinegar, but use caution: There can still be a bit of sting if there are open areas of skin. If there are any skin cuts or wounds, using full-strength milk topically in a compress is also an option.