Red lines on the arm are mainly considered to be a sign of superficial phlebitis. Superficial phlebitis is an aseptic inflammation of the blood vessels, which is different from the inflammation caused by infection in the traditional sense. When superficial phlebitis is present, it is mainly characterized by local pain, red skin color, increased temperature, and red streaks along the vascular pathways, which are less elastic and harder to the touch. In severe cases, exudation and infection may appear on the surface of the blood vessels. When superficial phlebitis appears, it is recommended to visit a specialized vascular surgery department for a clear diagnosis and give symptomatic treatment under the guidance of a specialist. At present, the main treatment is to reduce the irritation factors, such as avoiding standing for a long time, avoiding repeated punctures, changing the infusion site, etc.. At the same time, magnesium sulfate can be applied externally or mucopolysaccharide polysulfate cream to improve the symptoms of phlebitis.