Vitamin E oil does NOT help stretch marks.
Clinic evidence does not support the claim that lotions or oils, such as vitamin E oil will help with stretch marks. ("Pregnancy: Stretch Marks, Itching, and Skin Changes", cancer.darmouth.edu)
What Causes Stretch Marks?
Stretch marks, medically referred to as striae gravidarum, are caused by excessive stretching of the skin and an increase in production of the hormone cortisone. The cortisone is believed to weaken the elastic fibers in the skin that subsequently ‘tear' when stretched. ("Stretch Marks: Causes", mayoclinic.com)
Promising Stretch Marks Research
Good news for those prone to stretch marks. Topical trentinoin may help to reduce the appearance of early stage stretch marks. A study published in the Archives of Dermatology investigated the response of early, clinical, active stretch marks to topical trentinoin, rentinoic acid. Study participants applied the topical cream or a placebo for six months. Measurements taken after two months of therapy revealed a marked improvement in the stretch marks of those using the topical trentinoin compared to those using the placebo. After six months, 80% of the those using the topical trentinoin had a definite or marked improvement concluding that the therapy significantly improves the clinical appearance of early, active stretch marks. (Kang, 519)