Analysis: Once upon a time a century-and-a-half ago, to be exact (see below) dredging a minor burn with ordinary wheat flour was considered an acceptable medical treatment, even by some physicians. But so was dressing the wound with white lead paint, oily poultices, and turpentine-soaked cotton. All these treatments were discredited and abandoned as medical knowledge progressed.
Current medical sources such as the Mayo Clinic and the American Red Cross advise treating a minor (first- or second-degree) burn by immersing it in cool water, then covering it loosely with dry, sterile gauze. Scientific studies have proven these measures effective.
The purpose of running cool water over the burn is to draw heat away from the skin, reducing swelling and pain. The purpose of a sterile bandage is to minimize air flow over the wound (which can exacerbate pain) and to protect the skin should blistering occur. It stands to reason that covering burned skin with refrigerated flour might produce some of the same benefits, but it could also cause complications (if your skin begins to blister, do you really want it coated with unsterile flour?). Why take risks with an outmoded remedy?
There's no scientific reason to suppose (and certainly no peer-reviewed studies to prove) that plunging your scalded limb into a bag of cold flour will lead to a better prognosis than immersing it in cool water and applying a proper bandage.
Beware of all medical advice that arrives via forwarded email.
http://urbanlegends.about.com/od/medical/a/Flour-For-Burns-Home-Remedy.htm