Psoriasis may be associated with viral infections, cellular immune response. Psoriasis is mostly related to genetics, environment, and immune abnormalities. The difference between pityriasis rosea and psoriasis is different in the site of onset, manifestation of skin lesions and course of the disease. 1. Onset site: pityriasis rosea mostly occurs in the proximal part of the limbs and trunk. Psoriasis rash can spread to the whole body, especially the elbow, knee and sacrococcygeal area. 2. Lesions: pityriasis rosea lesions are oval rose spots, consistent with the skin texture, covered with furfuraceous scales. Psoriasis begins with red papules or macules, gradually expanding into red plaques with clear boundaries, which can be in the form of dots and drops, plaques and other forms, and covered with a thick layer of silvery-white scales. 3. Duration: pityriasis rosea has a short course and is self-limiting, generally 6-8 weeks to subside on its own, most of which will not leave scars. Psoriasis has a long course and is generally incurable and prone to recurrence. When the above symptoms occur, it is recommended to consult a doctor in time, follow the doctor’s instructions for further examination, clarify the cause with the help of the doctor, and carry out targeted treatment or therapy.