A unique rash of poison ivy cases in Pennsylvania has left patients and their doctors puzzled.

While poison ivy contact is usually characterized by redness, five Pittsburgh victims have found itchy black spots that have been determined by doctors to be a subtype of common poison ivy.

“We had a child come in and thought it was a mole, because it was so black,” Dr. Douglas Kress at Children’s Hospital told CBS affiliate KDKA. “We had another child come in. I thought it was a severe reaction to a spider bite. Then, as the disease progressed, it became clear it was poison ivy."

Click here to read the KDKA report.

Kress said that the unfamiliar marks found on five different patients were due to the plants’ formation of a “stickier” resin that boroughs deeper into the skin than typical poison ivy does. He attributed the change in resin texture to humid weather.

Kress also told KDKA that anti-bacterial creams and calamine lotions that clear up a normal case of poison ivy within days will also cure the “black dot poison ivy.”