Help and support Frequently asked questions Treatment FAQs Why have my botulinum toxin injections stopped working? The effectiveness of the injections can vary for a number of reasons including how long you’ve been having them for, how large a dose you are given, how long it was since you last had injections and how severe your dystonia is. To understand why your injections are not working, and if changes are needed, you must discuss this with your injector. It can be helpful to document the following information to help your discussion: percentage of improvement after the injection how long the benefit lasted after the injection side effects after the injection what has improved and what has not improved after the injection In rare cases people can become immune to the toxin (only a few percent of all those being injected) so for most people, where the injections are not working there is another explanation.