The short term side effects are due to the diffusion of the BoNT-A from the site of injection to adjacent muscles . They occurred about 10 days after the injection. The location of the injection will determine the type of side effects. . The dose and the injection technique are important in reducing the risk of side effects.

In case of injections:

  • around the eye :droopy eyelid (ptosis), blurred or double vision, exposure keratitis and tearful eye.
  • around the neck and the jaw: swallowing difficulties which can require for the patient soft diet and great caution when eating or drinking. Patient has to contact the doctor who had performed the inejctions, to assess teh severity of the swallowing difficulties and the possibilty of choking and aspiration pneumonia.Rarely patients have to be admitted to be fed via a nasogastric tube for about 1 or 2 weeks, the time that the swallowing becomes safe again.
  • around the face: droopy lip, lopsided smile.
  • around the forearm: weakness in the hand grip, weakness of fingers flexion or extension.around the vocal cords: quiet voice, up to loosing the voice, swallowing difficulties for fluids.

All these side effects are always transient and will disappear in 4 to 6 weeks time; there is no permanent effect of weakness , following the injections.

The FDA issued a warning in 2008-02009 about  pediatric  adverse event case reports; “botulinum toxin products were mostly used to treat muscle spasticity in cerebral palsy, a use that has not been approved by the FDA. The reported cases of spread of botulinum toxin effect beyond the site of injection were described as botulism, or involved symptoms including difficulty breathing, difficulty swallowing, muscular weakness, drooping eyelids, constipation, aspiration pneumonia, speech disorder, facial drooping, double vision, or respiratory depression.  Serious case reports described hospitalizations involving ventilatory support and reports of death.” Treatment of children spasticity should be performed only by specialised peadiatric rehabilitation teams.

Flu-like symptoms have been reported by patients.

Long term side effects have not been observed and patients have been injected for more than 10 years ( published studies) and sometimes up to 20 years ( personnal datas) without any permanent neurological complications.

There are contra-indications in patients with defective neuro-muscular transmission (e.g. myasthenia gravis), and in association  with drugs interfering with the neuromuscular function (e.g. aminoglycosides, curare-like non-depolarising blockers) . BoNT-A has been injected  during pregnancy in case of severe dystonia but caution is recommended as there is only anecdotical reports but no toxicity data on BoNT-A and pregnancy.

Detailed explanations about the side effects can be found in Dr Marion’s blog,, written for patients.

in case of swallowing difficulties:

Swallowing difficulties after Botox injections.What to do and how to avoid them.

in case of droopy eyelids or double vision

Droopy eyelid, double vision..after Botox injection, what to do?