Facial exercises do not tighten skin, according to plastic surgeon Bryan McIntosh. It is possible that facial skin can shrink after losing weight, leading to the appearance of tighter skin.
No research exists to prove or disprove the effectiveness of facial exercise for cosmetic purposes, according to Dr. Murad Alam of Northwestern Feinberg School of Medicine. Facial exercises may work to temporarily relax muscles and delay minor wrinkling of the skin in the same way that Botox works by paralyzing muscles, according to Slate. Wikipedia explains that facial exercises are sometimes used as part of physical therapy to prevent muscle loss caused by stroke, aging or facial paralysis.