• Infection
• Poor blood supply (ischemia) 
• Presence of foreign material
• Presence of necrotic tissue
• Movement in injured area
• Irradiation
• Tension in injured area

• Advanced age
• Protein malnutrition
• Vitamin C deficiency
• Zinc deficiency
• Corticosteroid excess
• Decreased number of neutrophils or macrophages 
• Diabetes mellitus
• Cytotoxic (anticancer) drugs
• Severe anemia
• Bleeding disorders
• Ehlers-Danlos syndrome