Compared with the upper face, the lower face is a less common focus for treatment with botulinum toxin. However, with proper attention to muscular anatomy and function, the results of treatment in this area can be rewarding. Aging skin loses both its elasticity and thickness. These physiologicalchanges, coupled with repeated pleating and contraction of skin, result in rhytids (wrinkles).

In the upper face, relaxing the relevant underlying muscles of facial expression with botulinum neurotoxin (BoNT) injections will eliminate the so-called dynamic rhytids (wrinkles) and, over time, will soften the appearance of static rhytids. In the lower face, the cosmetic effect is less about the elimination of the wrinkles and more about changing appearance, often through paralyzing target muscles to allow unopposed action of complementary musculature. This approach can be useful, for example, to help correct age-related drooping of the nasal tip or the corners of the mouth. This chapter illustrates in detail the anatomy of lower facial muscles and specific injection sites, and discusses injection patterns to achieve specific results.