Glabellar lines are caused by the stress exerted on the skin by hyperactive corrugator muscles. As the skin ages, it loses its ability to withstand the pressure of these muscles and yields by developing wrinkles. In addition to this, glabellar lines can also develop as a result of a number of lifestyle choices, including:
sunburn history
smoking
severe or chronic dehydration
significant or continuous stress
diets lacking in healthful fats, antioxidants, and other vital nutrients
poor skin care