<s>[INST] My husband has been using a heating pad on his lower back and the skin has developed a mottled appearance, which seems to be getting darker. He is also diabetic. Should he be concerned? Obviously he s not. [/INST] Dear Shamballa, Thanks for contacting hcm From the history you are giving , it seems to be grade 1 burns that have been caused due to heating pad. You must stop using the heating pad on his back and  consult your Plastic Surgeon or post his pictures, along with his  HB1Ac levels tha will tell about  his  blood sugar maintenance levels in past few months. </s>