Psoriasis occurs in all age groups. Birth morbidity has been reported, most recently at the age of 108, and it appears that it can occur in infants as young as very early in life, and in old men as big as snapshot. Results from several studies have shown that the majority of patients had their first psoriatic rash between the ages of 20 and 30. Another study of 2,400 patients found that the first peak of the disease was around 22 years old and the second peak was around 55 years old. More than 70% of patients with the first onset of psoriasis are aged between 20 and 50 years old, which means that the age of the first onset of psoriasis is still more common in young adults. In the study of 245 children, the average age of onset was 12.5 years. Early onset (before age 15) may indicate more severe illness in terms of rash area and response to treatment. At the same time, the earlier a case occurs, the more likely it is to have a similar history in the family.

        Psoriasis can be divided into four types: vulgaris, pustules, arthropathies and erythrodermis. Psoriasis vulgaris is the most common type, accounting for more than 95% of the total number of patients with psoriasis. Although the other types have severe symptoms and cause great damage to patients, the overall number of cases is relatively small.