Flu-like symptoms following botulinum toxin therapy

► FLS have been reported in between 1.7% and 20% of patients treated with BoNT type A. ► FLS have been reported in between 5% and 55% of patients treated with BoNT type B. ► FLS usually appear within the first two weeks of BoNT administration. ► Risk factors for the development of FLS after BoNT treatment have not yet been identified. ► Bacterial peptides without neurotoxin properties may play a role in the pathogenesis of FLS.