Lines in the face are caused by the natural ageing process of the skin, external influences (e.g. exposure to sunlight) and lifestyle choices (e.g. smoking). Another major factor in the formation of lines is the mimic activity of the small muscles under the skin, which we often use subconsciously like when we furrow our brow.
Botox and hyaluronic acid are the most successful methods for the non-surgical correction of lines. The Botox treatment is discussed under