The sensation of ice on the skin after injection of any sort is soothing.  Practitioners have used ice after the injection of botulinum toxins in the face, hands, underarms, feet etc reduce discomfort.  However, there maybe a potential drawback that may outweigh the benefit.

Uptake of botulinum toxin by the motor neurons is an energy dependent process.  Ice decreases the temperature of the skin and underlying soft tissues such as  muscles.  A decrease of temperature by about 10 degrees C will drop the rate of metabolism by about 50%.  Icing may result in drop of temperature from 37 to 7 ‘C which may result in upto an eight fold reduction of metabolic rate (Personal observations / unpublished observatons – KCS, D Schachter, R Schachter)

Though for most cosmetic injections ice is only applied for a short period of time it may still have effects on the uptake of botulinum toxin,  further clinical studies are required to establish accurate data.