How long are botox toxins in your body? Do they diminish at once, or gradually over time?

The results of your Botox will disappear gradually in about four months or so. It's doesn't just disappear all of a sudden. Usually, Botox injections can be scheduled every 4 months or so, depending on the area and how you react to the treatment.

Typically botulinum toxin is broken down in three months.  There is no evidence it goes other than where it is injected unless the dose is excessive. 

It is very uncommon for botulinum neurotoxins to enter the systemic circulation.  When used for intradermal/muscular injection on the face or neck, they are quickly taken up by the muscle cells and work at the cellular level to block neurotransmission.  There have been reports of spread of the toxin at a distant site from injection, but studies done on blood after injection have shown nothing of concern.  Hope this answers your question.  Best, Dr. Emer.