What causes stretch marks?
Stretch marks are caused when the skin is stretched to the point of breaking down, similar to elastic losing its' elasticity. Losing collagen and elastin in the skin causes stretch marks, loss of tone, fine lines and wrinkles. When there is a breakdown or loss of elastin and collagen fibers or excessive stretching in the skin, the mark actually shows through to the
epidermis (top layer of skin).
Stretch marks often occur in the normal course of development especially in women. They are frequently aggravated by rapid growth, pregnancy, hormones and some other natural causes. Severe stretch marks can be caused by some medications including steroids such as cortisone. Stretch marks are weaknesses in the supporting structure of the skin causing layers of the skin to separate leaving the skin grooved and discolored. Stretch marks develop when the skin is excessively stretched during pregnancy, weight gain or growth spurts. Dermal collagen is damaged and blood vessel dilation results in the formation of red or purple-colored early stretch marks. Inflammation and collagen remodeling may lead to the loss of pigment-producing melanocyte cells or obscuring of melanin pigment. Over time, this lack of pigment results in the white or hypopigmented scars that most people associate with mature stretch marks.
One theory is that they develop when the skin is stretched to the point of breaking down, due to a dramatic increase in the size of tissue. This stretching of the skin is similar to elastic losing its elasticity. The actual stretch marks develop in the middle, elastic layer of the skin, called the dermis. It is made up of fibers called collagen that allow your skin to stretch and then shrink back into shape. If this layer of skin is continuously stretched over a long period of time, the elasticity breaks down and the skin tries to remedy the problem by increasing the amount of collagen in the over stretched area. This is what then creates the scars in the dermis which show through to the epidermis (top layer of the skin).
The stretching of the skin can come about from rapid weight gain over a short space of time, such as during pregnancy. Stretch marks can also be found on children who have become quickly obese or on adolescents who have had a growth spurt during puberty. Athletes and body builders can also develop stretch marks due to constant repetitive exercises. The most common areas affected by stretch marks are the hips, breasts, buttocks, thighs and abdomen. However, some believe that the term stretch mark is a misnomer and they are not caused by the stretching of the skin at all. It has been suggested that stretch marks are caused due to an increased level of a hormone called glucocorticoids, circulating through the bloodstream. This hormone is secreted by the adrenal glands and it is increased during pregnancy, adolescence, with obesity, Cushing’s disease and weight lifting. The glucocorticoids affect the dermis by preventing the fibroblasts from forming collagen and elastin fibers that are required to keep growing skin taut. Dermal tearing then follows as there is a lack of supportive material when the skin is being stretched. So the stretching may determine where the stretch marks will occur but the actual stretching is not seen as cause of stretch marks. It has also been suggested that some people are more genetically prone to stretch marks than others. Skin type may be a factor; dryer skin has less elasticity than oily skin, and more prone to stretch marks. Stretch marks can also develop more easily in skin with a high proportion of rigid cross-lined collagen that occurs in teenagers.
Another theory on the cause of stretch marks is that they can occur due to the abnormal collagen formation as a result of medications or chemicals that interfere with collagen formation. It is also suggested that some medications that are hormonal or steroid based may cause stretch marks.