Pityriasis rosea (PR) is a benign rash that usually begins as a large circular or oval spot on your chest, abdomen, or back. The circular patch known as the herald patch can be up to 4 inches wide. These kinds of patches are often triggered by a viral infection, mostly among children and young adults. The patches are widespread, minimally itchy, skin rash on the abdomen, back upper, legs and upper arms. It may appear 4-5 days after the onset of the symptoms and continue to appear for a while.