Synopsis
Recognise the herald-patch and cleavage-line eruption, identify pregnancy and diagnostic exceptions, exclude tinea or secondary syphilis when indicated, and avoid overtreating a self-limiting rash.
- Pityriasis rosea often starts with one 2 to 5 cm scaly herald patch on trunk or proximal limb, followed days to two weeks later by many smaller oval scaly lesions.
- Secondary lesions align with cleavage lines, forming a fir-tree distribution across the back; a herald patch is helpful but not present or recognised in every case.
- On brown or black skin, lesions may be deep brown or have a lighter border rather than look pink, and post-inflammatory lighter or darker marks may last for months.
Key red flags
Pregnancy with a new pityriasis-rosea-like rash needs immediate maternity or clinical assessment because early-pregnancy disease has been linked with miscarriage and preterm birth.
A new rash in pregnancy must not be self-labelled. NHS advises immediate contact with maternity care, GP or NHS 111 because early-pregnancy pityriasis rosea has reported adverse associations.
Investigation priorities
Confirm a herald lesion followed by cleavage-line secondary eruption and identify atypical palms, soles or mucosae.
Management branches
Classic herald sequence and cleavage-line rash in a well, non-pregnant person without atypical sites.
- Explain that the eruption is not usually contagious, often peaks before improving, and commonly settles in six to eight weeks or within a few months without scar.
- No active treatment is needed if comfortable; continue school, work and ordinary contact, and avoid irritant soap or unnecessary antimicrobial treatment.