The actual causes of stretch marks are still largely unknown. Fundamentally, the depletion of collagen causes skin integrity to reduce and the end result can be stretch marks. The rupturing of minute blood vessels is also involved in causing the earliest pink discolorations of such blemishes.

Apart from the most obvious reasons, there is now an evolving belief that abnormal hormonal activity can also lead to stretch marks. If this is true, their exacerbation in puberty and pregnancy may be for more than purely physical reasons. In fact, there seems to be evidence that hormonal changes brought on by major depression can also cause the problem. Additionally, the use of steroids can cause and exacerbate it.

Rapid weight gain or loss is an established cause of stretch marks, and the most conscientious regimens that now exist take the possibility of stretch marks into account. Of course, the bodily changes during the growth processes of puberty are an established factor.

Among the lesser known causes of stretch marks is poor nutrition. A diet that lacks sufficient proteins, carbohydrates and fats is strongly believed to contribute to their development, as is deficiency of vitamins A, E and C. It is also essential that one's food contains enough zinc, since this element produces collagen - which basically holds the skin's tissues together in the first place. However, an excessive intake of zinc can cause acne in certain skin types and professional guidance should be sought as far as zinc supplements are concerned.

There may be hereditary factors and quite simply skin types involved in the formation of stretch marks, but this is a gray area and only further research will establish whether these are indeed valid causes.

An abrupt change in geographical environment - especially where extremely cold, hot or dry climactic conditions are involved - may contribute to an earlier-than-usual onset of stretch marks.