After botulinum toxin is injected into the masseter muscle, the effect generally lasts for about 6-8 months, and the masseter muscle will gradually recover after the drug effect is lost. However, after repeated injections, the effect will be more and more lasting, generally lasting about 1 year after 3-4 injections, and a few people can maintain the masseter effect even without injection in the future. Botulinum toxin can be injected repeatedly without toxin accumulation.