Will eating after Botox on masseter decrease the effect and can you do another injection in 3 weeks?

Dear iamamermaid:
Chewing immediately after Botox is injected works the masseter muscles and at least theoretically may increase the uptake of Botox by the neuromuscular junctions such that more Botox is taken up and less diffuses away.  But excessive chewing, such as chewing gum for hours a day, may actually increase the size of the masseter muscles,
Usually an effect is seen by one week, but if your muscles are very large, you may not see much benefit from your first treatment, in which case more should be injected 7 to 14 days later.  As you continue your treatments (approximately every four months), you will see more of an effect from the same dose. Therefore, the dose may actually be reduced over time.
All the best,   Dr. Clark

No, chewing won't negatively impact your results. It can take 1-2 weeks for final results with Botox for masster reduction. If you're unhappy with your final results, you can have a touch up of Botox. See an expert. Best, Dr. Emer

You can go back to your provider and discuss your desire to have more Botox injected. If you believe that you need more vials, then it needs to be at least 10 dys after your first injection, so your injection site is not swollen. It takes time to see Botox effects with the masseter muscles. It is hard to give you any precise opinion without picture provided. Discuss this with your provider. Good luck!