What Does A Poison Ivy Rash Look Like?

Hi Doctor - I just went to an urgent care clinic last night to have a case of poison ivy evaluated. The affected area is along the side of my arm, fairly close to the wrist. I can deal with the discomfort, swelling, redness, etc, but what prompted me to seek attention was the fact that a red streak under my skin runs from the area affected by the ivy towards my armpit, presumably toward a lymph node. The doctor was unconcerned, though prescribed oral prednisone and a topical cream for the rash. My temperature is normal, no other symptoms, etc. Is this ‘red streak’ a normal response to a significant patch of poison ivy? Searching the internet can yield scary results, like the streak is indicative of a ‘spreading infection’ in the lymphatic system. Again, i continue to feel well though, and starting the medications. Thanks for your feedback / opinion on this Doctor. Just wanted another opinion.