Red light therapy devices are not harmful if used reasonably. If not, it may cause the patient’s local symptoms to worsen. For example, if a patient starts using red light on his local irradiation within 48 hours after the appearance of trauma, it may aggravate local bleeding as well as swelling. If red light irradiation is used 48 hours after the injury, it may accelerate local blood circulation, which may lead to rapid reduction of swelling, which is beneficial to the patient at that time. Irradiation of other areas, such as postoperative moist wounds or pressure sore wounds, will accelerate local symptom relief and even local wound healing.