There are two main reasons for face swelling after tooth extraction: anesthesia and tooth extraction trauma. During anesthesia for tooth extraction, the injection needle easily pierces the blood vessels causing bleeding in the tissues, especially when deeper injection anesthesia is performed, such as maxillary nodal conduction block anesthesia, it is easy to pierce the pterygoid plexus vessels, forming a hematoma and causing facial swelling. The trauma caused by tooth extraction also tends to cause facial swelling. Tooth extraction leaves small wounds in the alveolar sockets and periodontium, and when there are wounds, they bleed and ooze. If there is oozing, there will be swelling. Guo Yuxing, Department of Maxillofacial Surgery, Peking University Stomatological Hospital So should I apply cold or hot compresses to swelling after tooth extraction? To answer this question, first of all, we have to figure out the process of the development of swelling. No matter it is facial swelling caused by anesthesia needling or facial trauma caused by tooth extraction trauma, the early stage is the exudation of blood and tissue fluid from the trauma, which is usually shown as exudation within 1-2 days after the trauma. The face is more prone to bleeding and exudation than other places due to rich blood flow, and therefore also more prone to swelling. starting from 3-4 days, there will be no more local exudation from the trauma, and the organism starts to absorb the exudate that exudes into the tissue interstitial space, and the absorption of these exudates depends on the macrophages in the blood. By understanding the development of swelling, we know that the question of whether to apply cold or hot compresses after tooth extraction is different in different time periods. After 1-2 days after surgery, it belongs to the exudation period, at this time, cold compresses are applied to constrict blood vessels, which can reduce tissue exudation and swelling, and after 3-4 days after surgery, it belongs to the absorption period, at this time, hot compresses should be applied to dilate blood vessels and accelerate the absorption of exudation. In short, blood circulation is like a logistics company. In the early stage of trauma, we slow down its operation by applying cold compresses to reduce exudation and swelling; in the recovery period, we accelerate its operation by applying hot compresses to speed up the absorption of exudation and promote the decreasing of facial swelling. This is not only for tooth extraction, but also for swelling caused by other trauma.