Blood flow to the skin of a normal foot can readily increase by 100 times if necessary, to conduct heat away from challenged areas. Impaired circulation and impaired endothelial dilatation (which are common in patients with diabetes) may make this increase in blood flow impossible, and the resultant burn may not cause pain if peripheral neuropathy is present.
My late mentor, Heinz I. Lippman, found that many patients with diabetes had burns of the feet after exposure to whirlpool baths set at 33.3°C (well below body temperature). In 1960, he gathered statistics on the reasons for amputation in the Bronx, New York, during 1959. Fully half of the amputations were performed because of infected burns in patients with diabetes.
Even if burns do not occur after hot-tub therapy, prolonged soaking in water causes maceration of skin. Macerated skin is more susceptible to injury and is less likely to heal than normal skin. Therefore, my colleagues and I advise all patients in our diabetes clinic to shower or bathe in cool water and to “get in, get washed, and get out.” We never prescribe foot soaks except sometimes for 5 or 10 minutes in potassium permanganate solution for fungal infections. We never use wet-to-dray dressings but occasionally use moist-to-dry saline dressings for wetting dermatitis.