Keloids are the result of abnormal wound healing. Normally, there is a balance between the production and the breakdown of collagen , which is a protein that makes up the fibres in the skin. With keloidal scars, the cells in the skin called fibroblasts produce excessive amounts of collagen. The collagen fibres are also thicker and wavier. This leads to the thick, raised appearance that is characteristic of keloidal scars. It is unclear what prompts this unusual healing process. Possible causes include genetic factors, skin tension, and the presence of a very high number of fibroblasts in the skin.