You're the Doctor - Answer
The patient in the photo below has Poison Oak (Rhus dermatitis). Don't feel bad if you missed it. She had 4 medical visits before it was successfully diagnosed.
Poison Oak is a form of a contact dermatitis (good work, "erp") and she actually contracted it while hiking in Point Reyes, California. Once the urushiol oil from the plant sets on the skin, an inflammatory and allergic response keeps it going, sometimes for weeks. The weeping blisters are common, as is the swelling redness. Contrary to common belief, the oozing blisters do not spread it. It is the underlying response of the body that keeps the dermatitis spreading.
She was successfully treated with topical and oral corticosteroids (Prednisone) but some scars have remained.
Thank you to K.M. for allowing her story and photo to be shared.