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Keloid scars are a result of an imbalance in wound healing. Normal wound healing in the skin reaches an equilibrium after six weeks to three months. At this stage, the production of collagen is matched by its degradation and remodelling. Any insult that can trigger an excessively long phase of collagen production compared to its breakdown has the risk of keloid formation.

Many agents have been thought to instigate a keloid scar. However, there have been reports of them arising de novo, with no prior injurious agent. This may simply reflect a forgotten, innocuous injury. Purported factors include:

  • tension when a wound is directly closed
  • trauma; theories as to how this triggers a keloid have included implantation of epithelial material, the attainment of a critical level of dermal inflammation and the disruption of the skin to a critical level within the dermis(1):
    • surgical incisions eg sternotomy wounds
    • tattoos
    • immunisations
    • thermal injuries
    • piercing, usually facial and commonly the ear, but can occur at other sites
    • foreign body implantation into dermis
  • general patholgy:
    • infection eg bacterial, viral - chickenpox commonly
    • acne

These insults are more likely to lead to a keloid scar in a genetically-predisposed individual as dictated by factors such as age, gender and even site on body surface (see predisposing factors submenu).


(1) Dunkin CS, Pleat JM, Gillespie PH et al. Plast Recon Surg (2007); 119(6): 1722-1732.

Last reviewed 01/2018