[2] Classically, it begins with a single red and slightly scaly area known as a "herald patch".

[14][15] In addition to typical papules and scales, forms appearing as very large plaques (pityriasis rosea gigantea), urticaria, large blisters, patches resembling erythema multiforme, oral lesions, and various other appearances have been noted.

[15][8] Variations in distribution include inverted forms, with rashes on the face or extremities without appearing on the trunk, as well as more uncommon versions localized to the armpits, groin, or extremities (pityriasis rosea circinata et marginata of Vidal) or unilateral spread.

[22] Classical symptoms are usually straightforward to recognize, but the wide range of atypical forms may cause difficulty for the clinician in diagnosing some cases.

[7] If the diagnosis is in doubt, tests may be performed to rule out similar conditions such as Lyme disease, ringworm, guttate psoriasis, nummular or discoid eczema, drug eruptions, other viral exanthems.

[24] A biopsy of the lesions will show extravasated erythrocytes within dermal papillae and dyskeratotic cells within the dermis.

[22] According to this principle, medical treatment with ultraviolet light has been used to hasten resolution,[29] though studies disagree whether it decreases itching[29] or not.

[31] Oral erythromycin was found to be effective for treating the rash and relieving the itch based on one early trial; however, a later study could not confirm these results.

[22] PR is not viewed as contagious,[34][35] though there have been reports of small epidemics in fraternity houses and military bases, schools and gyms.