Wounds do not crust after applying erythromycin ointment, which may be due to drug reaction, wound infection, foreign body residue and other reasons. 1. Drug reaction: erythromycin can be used for wound anti-inflammation and prevention of infection, but erythromycin contains petroleum jelly sol, which, when applied to the wound site, may cause the patient’s local blood circulation to be poor, resulting in slower recovery and scabbing. 2. Wound infection: improper wound care can lead to infection, causing necrosis of the affected tissues, the formation of pus, increased secretion. It will cause the capillaries and newborn granulation tissue in the affected area to fail to grow, resulting in the occurrence of non-scarring. 3. Foreign body residue: improper wound debridement can cause foreign body residue in the wound, causing the body to have a rejection reaction, resulting in inflammation, so that the wound repeatedly does not heal the situation. There may be other reasons why the wound area does not scab for a long time, please go to the hospital for examination and treatment in time to avoid delaying the condition.