What is Pityriasis rosea?

Pityriasis rosea is a common, harmless skin rash that typically starts with a single larger patch, known as a 'herald patch', followed a few days to weeks later by smaller patches spreading across the chest, back, and abdomen, often in a pattern resembling a Christmas tree.

The exact cause isn't fully understood, though it's thought to be linked to a viral trigger. It's not considered contagious and usually clears up on its own within six to twelve weeks without leaving scarring.