Psoriasis is a recurrent erythematous scaly disease. It is a disease with a long history. It is commonly known as psoriasis in China. It is common to see a family with many patients from several generations. It can also be seen that identical twins suffer from psoriasis at the same time. This means that psoriasis is a genetic disease. Scientific research can now identify the psoriasis gene. The gene for psoriasis has multiple loci. It is a polygenic recessive disease. About 20-30% of patients have a clear family history. But there is also a large proportion of patients who do not have a family history. This is a characteristic of recessive genetic inheritance. Because it is a lesion of multiple loci. Therefore, the number and location of loci determines how early and how severe the disease will develop. It can be seen that some patients may develop the disease in infancy. And some patients develop the disease in old age. It is because psoriasis is a genetic disease. Scientific research cannot yet change and replace these genetic loci that have the disease. Especially after birth, it is difficult to change. However, it cannot be ruled out that the replacement of defective genes can be done in the future after scientific progress and development. Therefore, taking any medication, especially some of the advertised herbal medicines, cannot cure psoriasis. However, drug treatment can control the development of psoriasis. This is because the development of psoriasis is related to the immune mechanism. Many drugs are immunomodulators, which are synergistic to control psoriasis.