Asymptomatic swelling of the right arm is related to the following causes: i. There may be inadvertent trauma, such as a contusion of soft tissues caused by the patient’s inadvertent impact with other objects during arm waving, or after having an inadvertent sprain, swelling of the right arm may occur. Second, there may be a case of cold. If the right arm is exposed to cold objects for a long time, it may lead to sterile inflammation here, and then cause swelling. Long-term pressure is common when the patient sleeps on the table or sleeps on the right side, causing long-term pressure on the right arm, which may cause swelling here. Fourth, it is caused by the relatively rare shoulder-hand syndrome, which is caused by trauma, heart attack, or brain-related lesions, resulting in sudden pain, limited movement, and swelling of the right upper extremity of the shoulder joint. This condition may also be caused by skin surface lesions, such as allergies, contact dermatitis, or insect stings.