Question about Dysport side effects, how long will they last?

Dysport stops working for most between 3-6
months. It is rare but sometimes patients can experience flu like symptoms
after a neurotoxin injection. It might be that you already had a virus going
through your system though. Especially if you had it before without any
symptoms.

If you've had the treatments before with no issues, I'm a bit surprised. It could be coincidence and you were already on the verge of some sickness and getting Dysport isn't the issue. Some people can get a headache after Dysport (or Botox) but it goes away pretty quickly. Did you go to the same injector all of the times your treatments were done? I'd suggest a follow-up with your injector to discuss. "This answer has been solicited without seeing this patient and
cannot be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."