Might try posting on both Dermatology forums too. Did your doctor/s tell you the type of rash? This would help narrow down a treatment search. If it's fungal and something like Tinea Versicolor a friend used Selsun Blue. Selsun Blue contains selenium sulfide which is an anti-fungal ingredient. Good luck
Hello,
Welcome here.
Aside from WaveRider's advice, which is good, the most important thing to control skin problems for people with diabetes is for you to get good control of your blood sugar.
High sugar means your skin is "sweet" and fungi and yeast infections can thrive under such condition.
How is your blood sugar? What is your HbA1c?
Please work hard to control your sugars. Please post any related questions so we may provide further information.