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What the label lists and what reports show

Botulinum toxin type a side effects

Botulinum toxin type a's FDA label: “The most common adverse reactions (≥4%) were tooth extraction, dry mouth, diarrhea, and hypertension.” FAERS holds 97,018 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is headache (5,925 reports).

  • No generic listed
  • Boxed warning

Check it at the source: the botulinum toxin type a FDA label on DailyMed (effective July 10, 2026); the FDA FAERS public dashboard.

What does the label list?

From the label: adverse reactions

The most common adverse reactions (≥4%) were tooth extraction, dry mouth, diarrhea, and hypertension.

Table 12: Adverse Reactions (≥5%) and Greater for XEOMIN than Placebo: Double-Blind Phase of the Placebo-Controlled Blepharospasm Study 2

Adverse ReactionXEOMIN (N=74) %Placebo (N=34) %
Eye disorders3821
Eyelid ptosis199
Dry eye1612
Visual impairment including vision blurred126
Gastrointestinal disorders3015
Dry mouth163
Diarrhea80
Infections and infestations2015
Nasopharyngitis53
Respiratory tract infection53
Nervous system disorders149
Headache73
General disorders and administration site conditions119
Respiratory, thoracic and mediastinal disorders113
Dyspnea53

Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.

From the label: adverse reactions, continued

The following adverse reactions to XEOMIN are discussed in greater detail in other sections of the labeling: Spread of Effects from Toxin [see Warnings and Precautions (5.1) ] Lack of Unit Equivalency between Botulinum Toxin Products [see Warnings and Precautions (5.2) ] Hypersensitivity Reactions [see Warnings and Precautions (5.3) ] Dysphagia and Breathing Difficulties [see Warnings and Precautions (5.4) ] Corneal Exposure, Corneal Ulceration, and Ectropion in Patients Treated with XEOMIN for Blepharospasm [see Warnings and Precautions (5.5) ] Risk of Ptosis in Patients Treated for Glabellar Lines [see Warnings and Precautions (5.6) ] Human Albumin and Transmission of Viral Diseases [see Warnings and Precautions (5.7) ] The most commonly observed adverse reactions at rates specified below and greater than placebo are: Chronic Sialorrhea: Chronic Sialorrhea in Adults (≥4% of patients): tooth extraction, dry mouth, diarrhea, and hypertension ( 6.1 ) Chronic Sialorrhea in Pediatric Patients (≥1% of patients): bronchitis, headache, and nausea/vomiting ( 6.1 ) Spasticity: Upper Limb Spasticity in Adults (≥2% of patients): seizure, nasopharyngitis, dry mouth, and upper respiratory tract infection ( 6.1 ) Upper Limb Spasticity in Pediatric Patients (≥3% of patients): nasopharyngitis and bronchitis ( 6.1 ) Cervical Dystonia (≥5% of patients): dysphagia, neck pain, muscle weakness …

Source: FDA drug label, Merz Pharmaceuticals, LLC, effective July 10, 2026 (SPL set ccdc3aae-6e2d-4cd0-a51c-8375bfee9458), via openFDA; the full label on DailyMed

What do FAERS reports show?

97,018 reports list botulinum toxin type a among the medicines taken, each a report of something that happened, not proof the medicine caused it; 4,022 are coded as a death and 7,448 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 19 reactions below, 11 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.

Reports received each year

The 25 most reported reactions

  • Drug Ineffective (a use or a product term, not a reaction)32,992
  • Off Label Use (a use or a product term, not a reaction)18,186
  • Headache (named in the label)5,925
  • Therapeutic Response Decreased5,273
  • Product Preparation Error4,398
  • Injection Site Pain (named in the label)4,226
  • Eyelid Ptosis (named in the label)3,778
  • Migraine (a use or a product term, not a reaction)3,477
  • Nausea (named in the label)3,304
  • Pain3,126
  • Dizziness (named in the label)2,966
  • Fatigue2,944
  • Multiple Use Of Single-Use Product2,860
  • Muscular Weakness (named in the label)2,847
  • Dyspnoea (named in the label)2,451
  • Dysphagia (named in the label)2,319
  • Asthenia2,309
  • Hypoaesthesia2,159
  • Rash (named in the label)1,934
  • Wrong Technique In Product Usage Process (a use or a product term, not a reaction)1,913
  • Product Use In Unapproved Indication (a use or a product term, not a reaction)1,911
  • Neck Pain (named in the label)1,842
  • Death (an outcome recorded in the report)1,835
  • Paraesthesia1,824
  • Vision Blurred (named in the label)1,809

Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms

What next?

Botulinum toxin type a: the full record
label, generics, price, shortages, recalls
Side effects hub
the most reported medicines and reactions