Stretch marks occur more frequently on women than men. But they do occur in both sexes. Common causes are weight gain, sudden shape changes and hormonal changes. The supportive network of collagen and elastin in the skin is broken down in the skin.
Microscopically the undulating ridges that occur between the two layers of the skin, the dermis and epidermis, are lost in the area, appearing as a flattened areas (as if the ridges have been stretched out).
As would be plain to anyone who has stretch marks, there is a lot of variation in their presentation. From flat, narrow, white marks, to red to purple coloured hollows in the skin, to others with a tough core in the middle of them. The differences are related to the underlying loss of structure and reorganisation, and the age of the stretch mark.
Most treatments used so far have not been very successful. We note what is used in the treatment section.