I Believe I Came In Contact With Either Poison Sumac

I believe I came in contact with either poison sumac or poison oak while weeding a vertical bank. Itching, blisters and small red bumps appeared the evening after a.m. gardening. I have been using Cortisone 10 cream and warm, soapy water rinses but the pain, deep itching and tiny blisters have a white, milky discharge when rubbed and do not seem to be diminishing. Sleep is interrupted several times during the night with pain and general discomfort. I am considering a visit to my M.D. but if this "malady" just needs to run its course, I'm not sure the best course.