Stretch marks or straie are generally the result of skin having been stretched beyond its elastic limits for prolonged periods of time. They become evident after massive weight loss.
They can also occur during rapid periods of growth such as in puberty.
Typically they occur because of fractures within the deepest layer of the skin, known as the dermis. In this regard, they can be considered a form of a scar.
They are notoriously difficult to treat.
Non-surgical approaches include techniques to improve their appearance with skin resurfacing using lasers or Plexr.
If the straie occur with loose skin, then surgery to remove the loose skin is often advised in terms of body contouring procedures.