Why does Botox spread from injection site? Under-diluted, too much, or treatments too close together?

Thank you for your excellent question.  Botox comes to your injector's office as a dehydrated powder that becomes reconstituted with normal saline.  The injector has discretion in how much normal saline is used in order to control the degree of dilution.  Because the units of botox determine effectiveness of treatment the dilution is important to know because the more saline used, the more fluid injected for the same number of units and the greater spread of the fluid from the site of injection, possibly leading to complications.  Hope this helps. 

Botox is a liquid solution injected under the skin. As it gets absorbed it can spread about 1 cm or less than half an inch. Deep massage can increase the spreading distance, but it's still a short distance. When diluted, more fluid is injected per unit of Botox, giving it more potential to spread in the tissues. All of these factors together contribute to spread from the injection site. It's important to seek out a trained injector who standardizes the dilution, so the amount injected is consistent. When in doubt, ask your injector about the concentration they use. I encourage my patients to ask as many questions as they need to feel knowledgeable and safe.