Pityriasis rosea is a mild skin condition in which a rash of scaly-edged pink spots or patches appears on the body and upper arms. It mainly affects children and young adults. The cause of pityriasis rosea is unknown. The first sign of this condition is a large, round spot—called a herald patch—on the body.
The rash typically appears a week later and may cause itching.
The rash usually lasts for 4 to 8 weeks and clears up without treatment, although moisturizers, or prescribed topical corticosteroids or antihistamines, may relieve symptoms.