The occurrence of psoriasis is related to genetic factors, immune factors and environmental factors, and is not an infectious disease, so whether a child will get psoriasis is related to whether he or she carries susceptibility genes and whether he or she has the disease factors. Since psoriasis sometimes has a tendency to gather in families, it gives the illusion of being easily contagious. In fact, this tendency to gather in families is a manifestation of psoriasis related to genetic factors, rather than being easily contagious. In addition to genetic factors, environmental factors are also important factors in the development of psoriasis, also carrying genetic genes, some people will develop, while others do not, and the same person will develop in one place, to another place will improve. Psoriasis is usually more prevalent in the north than in the south. All these phenomena show that the onset of psoriasis is also closely related to environmental factors. In addition, immune factors are associated with the development of psoriasis, and the presence of immune cells and immune mediators can be seen in the lesions of psoriasis vulgaris. In addition to this infection, mental stress, trauma, alcoholism, smoking and the effect of certain drugs are often triggers of psoriasis. Therefore, psoriasis is not an infectious disease, but a common recurring chronic inflammatory skin disease, related to genetic factors, immune factors and environmental factors.