The clavicle has lines like dirt, which may be caused by the following aspects: 1. There may be dirt inside the pores here or pigmentation around the clavicle. The former is often due to the fact that the skin here has been exposed for a long time and the wind has caused a large amount of dirt to be deposited inside the pores, while the latter is often due to local inflammation and injury here, which then complicates the pigmentation here. 2. There may be normal muscular signs, such as a series of longitudinal muscles above the clavicle, such as the anterior oblique muscle, the middle oblique muscle, and the posterior oblique muscle. These muscles will have obvious bulges when the patient is emotionally tense or when the neck is retracted, and at this time at a distance, the patient will be mistaken to see lines similar to dirt. 3, may be superficial skin veins. Sometimes superficial skin veins look relatively dark at a distance and are easily seen around the collarbone, which can be easily mistaken for dirt-like lines.