Psoriasis is a common erythematous scaly skin disease characterized by epidermal proliferation and inflammation, and is a common chronic skin disease with a high incidence worldwide. The incidence is high in Caucasians, at 2%-5%, and in the Far East, the incidence is 0.1%-0.3%. China is characterized by a higher prevalence in men than in women, a higher prevalence in urban than in rural areas, and a higher prevalence in the north than in the south. The national average annual incidence rate in urban areas is 0.2%. This is higher than the average annual incidence rate in rural areas (0.08‰) found in the same period. With industrialization in recent years, the incidence of psoriasis has been increasing. It is a polygenic genetic disease, and is affected by a variety of factors, such as trauma, mental, environmental, life, infection, etc. Stressful life events can affect the neurological, endocrine and immune systems, through these intermediary systems play a very important role in the onset and aggravation of psoriasis, and there have been more relevant studies in recent years. 1, infection factors Infection is one of the main risk factors for the development of psoriasis, mainly including bacterial and viral infections of the upper respiratory tract and fungal infections of the skin surface, etc. Currently, the most studied are streptococcal and Staphylococcus aureus infections, MallonE et al. on 29 cases of Caucasian whites with a clear history of sore throat (or) anti “o’ HLA I class C genotyping results in patients with punctate psoriasis with titers greater than 2ooT (noting d units showed that:HLA I Cw*0602 gene and streptococcal infection were associated with psoriasis. weisensee et al. showed that streptococcal infection was associated with the occurrence of type I psoriasis (age of onset must be ≤40 years; positive family history; positive for HLA antigens Cw6, B13, B57) closely associated with the occurrence of type I psoriasis (age at onset must be ≤40 years; positive family history; HLA antigen Cw6, B13, B57 positive). It is suggested that there is an abnormal immunogenetics of streptococcal infection in psoriasis patients, which needs to be studied more deeply at the molecular level; Bunse et al. used B. furfurans as a chemoattractant to observe its chemotaxis on polymorphonuclear leukocytes (PMN), and the chemotaxis of B. furfurans on PMNs of psoriasis patients was significantly higher than that of the control group, indicating the role of B. furfurans in the isomorphic response to psoriasis. The role played by B. furfurans in the isomorphic response of psoriasis. The study of various infectious factors including bacteria, viruses and fungi in the process of onset, recurrence and exacerbation of psoriasis will play an important role in the prevention and treatment of psoriasis. 2, genetic pathology In recent years, more and more complex disease susceptibility genes have been located and cloned, but there are still many issues to be studied in depth, psoriasis (Psoriasis) is one of them. There is often a family history of the disease and a genetic predisposition. 85% of early-onset cases (type I) have a family history of the disease with the HLA-1cw6 gene, while positive family history of late-onset cases (type II) is rare. Foreign reports of psoriasis have a family history of 10% to 90%, mostly around 30%, and domestic reports of 15% to 20%. Li Jing et al. identified seven psoriasis susceptibility loci (PSORS1-PSORSS7) by genome-wide scanning of genetic samples from different groups of psoriasis patients, of which PSORsl, a susceptibility locus located on chromosome 6PZI, is a current research hotspot, which includes three candidate genes, namely HLA-CW6, CDSN, and HCR. the role of each pair of genes When the cumulative effect exceeds a certain value, the disease will develop when there are certain exogenous factors or changes in internal factors. 3, mental factors psoriasis is a psychosomatic disease, some studies in recent years have clarified that mental tension and negative life events can induce aggravation of psoriasis, Farber et al. investigated 2144 cases of psoriasis patients, 40% of whom admitted that tension or anxiety aggravated the disease. Later, 5,600 patients were surveyed, and 30% of them still believed that worrying triggered the disease. Zhang Chunmin et al. reported that the scores of three psychological factors, depression, anxiety and terror, were significantly higher in patients with psoriasis than in controls, and Jiang et al. found that the distribution of substance P (sP) and calcitonin gene-related skin (CGRp)-positive fibers was more dense in the epidermis of lesions compared with normal controls. sp and CG stajun can chemotactic neutrophils and promote proliferation and division of keratinocytes and endothelial cells. SP can also activate T cells and induce endothelial expression of adhesion molecules, further aggravating psoriasis. In recent years, people have conducted more in-depth research on neuroskin and its receptors in the skin. 4, dietary factors In recent years, more and more attention has been paid to the role of dietary and behavioral factors in the occurrence, development and prevention of psoriasis. American Dr. Pegano proposed a natural treatment for psoriasis which is of great reference value, however, the living conditions and dietary habits abroad are many different from those in China, and the recipes recommended by Pegano cannot be copied. And nowadays, in Europe and America, the recipes have been greatly improved, while in our country, not much has changed. However, we should limit fried, greasy and salted foods, such as certain foods beef and mutton, sea fish have been proved to contain more arachidonic acid (AA) and affect the recovery of psoriasis, which can be appropriately contraindicated in the acute period; some patients are allergic to fish, shrimp and eggs, which are also contraindicated. MichaessonG has reported that some psoriasis patients have a history of unexplained gluten hypersensitivity reactions. When they consumed a gluten-free diet, their psoriasis improved significantly. Serwin et al. found that serum selenium levels in patients with psoriasis vulgaris were significantly lower than in the control group, and there was a negative correlation between serum selenium levels and disease severity in patients with disease duration of more than 3 years. It indicates that psoriasis is possibly associated with metaplasia and selenium. Therefore, a reasonable diet is the main measure for the treatment of psoriasis. 5, trauma factors Trauma generally refers to skin damage, physical trauma and mosquito bites, etc., which can stimulate psoriasis, which is called “Kocbner phenomenon” or “homoeopathic reaction”. The incidence of Kocbner’s phenomenon is reported to vary from 5 to 76%, and it mostly occurs in patients with type I psoriasis or high frequency of relapse at a young age during the progressive stage of the disease. If a patient reacts to a certain experimental stimulus, he will react to all stimuli; on the contrary, if a positive reaction cannot occur to a stimulant, he will fail to react to other stimuli as well. In recent years, a more comprehensive analysis and investigation of the relationship between trauma and psoriasis and its causative factors have been carried out, and special emphasis has been placed on scratching the skin lesions and certain inappropriate treatment measures as important causes of the “Kocbner phenomenon”, which should be taken seriously. 6.Climate factors Climate change, as one of the triggering factors of psoriasis, has been paid more and more attention by scholars. It is believed that most of the patients have aggravated or relapsed symptoms in winter and reduced or disappeared in spring and summer, which are called winter-type psoriasis; while a small number of patients with heavy summer and light winter are called summer-type psoriasis. In China, Tang Zhanli et al. explored the relationship between the onset of psoriasis and meteorological factors, and the single-factor analysis showed that the average annual temperature, average annual air pressure, average annual precipitation and average annual relative humidity were significantly correlated with the incidence of psoriasis. For example, total serum protein, albumin, hemoglobin and carbon dioxide binding capacity are higher in winter than in spring; blood pressure, gastric acid and corticosterone are higher in winter than in summer; globulin is higher in spring than in winter; and leukocytes are higher in winter than in summer, etc. However, whether climate change is related to these factors needs to be studied in depth. 7, endocrine influence Scholars have noted that endocrine changes are related to the development of psoriasis, Boxd et al. reported: 63.3% of women with psoriasis improved after pregnancy, 13.3% worsened, and 23.3% did not change. In this regard, Mowad et al. investigated the changes in psoriasis in 248 women with psoriasis after menstrual cycle, oral contraceptives, fertility drugs, hormone replacement therapy, pregnancy, and breastfeeding, and the changes were independent of age and severity of the disease, and the majority showed remission in the first 2 months after pregnancy. The same changes occur in 80% of those with multiple pregnancies, and 13% may have different reactions, but they are not related to intrauterine sex. 8, concomitant diseases Among the triggers for the development of psoriasis, there are often other diseases that start first and then induce or aggravate psoriasis, and there are also psoriasis that have already suffered from and then some other diseases, and domestic and foreign studies have confirmed that psoriasis patients are often accompanied by disorders of lipid metabolism. However, it is still inconclusive whether this disorder is primary or secondary to psoriasis, or whether it is the result of the use of drugs (such as retinoids), and the occurrence of hyperlipidemia and psoriasis may have a common genetic basis. The data show that obesity, hypertension, diabetes mellitus, hyperuricemia, fatty liver, liver function abnormalities and kidney damage may have factors associated with psoriasis with hyperlipidemia. At present, the pathogenesis of psoriasis is not fully understood, and significant results have been achieved in exploring the etiology of psoriasis and the factors affecting its prevalence. However, although some of the “contributing factors” have been elucidated, the prevention and treatment of psoriasis continues to challenge epidemiologists and clinicians to avoid these risk factors in order to reduce the occurrence, recurrence, or exacerbation of psoriasis.