Botulinum toxin acts at the synapses of the neuromuscular junction, inhibiting muscle contraction. By temporarily paralyzing the targeted muscles, wrinkles caused by repetitive muscle movement are smoothed over time. However, if unintended diffusion affects adjacent muscles, adverse effects such as eyelid drooping (ptosis), “samurai eyebrows”, or eyelid swelling may occur. For this reason, it is essential that botulinum toxin treatments be performed by a highly experienced and skilled physician. The effects of botulinum toxin treatment typically last for approximately 3–6 months.