Final answer:
Pityriasis rosea is a common skin condition characterized by an itchy, pink, scaly rash that usually starts with a single, large patch called the herald patch. The rash spreads along the skin's natural lines and is thought to be caused by a viral infection. It often clears up on its own without treatment.
Step-by-step explanation:
Pityriasis rosea is a common skin condition characterized by an itchy, pink, scaly rash that usually starts with a single, large patch called the herald patch. This patch is followed by smaller patches that spread along the skin's natural lines. Pityriasis rosea is thought to be caused by a viral infection, although the exact cause is unknown. The rash typically lasts for several weeks and then clears up on its own without treatment.