Botulinum Toxin injections are a treatment that works for most people when administered correctly. If it doesn't seem effective, the following reasons might be considered: Issues on the Medical Side Insufficient dosage If the dosage is too low, it can make the treatment less effective. Incorrect injection site If the injection isn't made in the appropriate muscle responsible for the wrinkle or if the injection depth isn't correct, it can reduce the effectiveness. Use of weakened potency medication If the formulation isn't prepared, stored, or managed properly, it can result in diminished effectiveness. Patient-related Issues Low sensitivity to Botulinum Toxin (Primary resistance) When the treatment doesn't show results from the beginning, despite being administered correctly, it's referred to as primary resistance. This occurs due to a low sensitivity to Botulinum Toxin, and it may require adjusting the dosage during touch-ups. Production of antibodies against Botulinum Toxin (Secondary resistance) If the treatment initially showed effects but the effectiveness diminishes over time, it's called secondary resistance. This is caused by the development of antibodies against the complex proteins or Botulinum Toxin contained in the formulation.