The most common reason Botox doesn't work is that it wasn't given in the right amount. Botox isn't a one-size-fits-all treatment and the same dose doesn't work for everyone. Some people may need additional Botox to achieve an effective level of muscle weakness. Botox can also be old, too diluted, or fake.
It's possible for some patients to develop a resistance to Botox, although this is rare. According to those who do recognize the phenomenon of resistance to Botox, the numbers are low: between 1 and 3% of patients who are injected will develop toxin-blocking antibodies. Can someone stop responding to Botox? The short answer is yes, but it's highly unlikely. Botox (and Dysport) are composed of proteins and our bodies are capable of detecting different types of foreign proteins and creating antibodies against them.
For example, gluten protein from wheat and egg albumin protein from eggs). Once recognized, these antibodies will circulate and neutralize Botox once injected, causing a loss of effectiveness. When the Botox bottle is opened and mixed, it must be used within a specified period of time, otherwise its effects may diminish. This is the approach used by many medical spas that have the cheapest price for Botox to attract customers.
Naturally, trimming the corners will give you a suboptimal result. If you're still not getting results, you may be one of those rare people who are “immune to Botox.” We see a lot of people who come to us from other places and tell us that “Botox doesn't work for me” or “I'm immune to Botox” and wonder what else they can do to treat wrinkles in the lines between the eyebrows, forehead and crow's feet. A more common occurrence is that some people develop tolerance to Botox after repeated use and tend to need to increase doses over time. Sometimes, people who didn't get an optimal result with Botox seem to respond better to Dysport or Xeomin.
Allergan points out that this occurs more often in people who receive frequent Botox injections or when used in higher doses, such as when treating cervical dystonia (although this is still less of a problem).