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OnabotulinumtoxinA Side Effects

In Summary

Commonly reported side effects of onabotulinumtoxinA include: antibody development. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to onabotulinumtoxinA: powder for solution

Along with its needed effects, onabotulinumtoxinA may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking onabotulinumtoxinA:

More common
  • Difficulty with swallowing
  • Difficulty with breathing or speaking
  • muscle weakness
More common—for blepharospasm
  • Dryness of the eyes
  • inability to close the eyelids completely
More common—for urinary incontinence caused by an overactive bladder
  • Bladder pain
  • bloody or cloudy urine
  • difficult, burning, or painful urination
  • frequent urge to urinate
  • lower back or side pain
Less common—for blepharospasm
  • Decreased blinking
  • irritation of the cornea (colored portion) of the eyes
  • turning outward or inward of the edge of the eyelids
Less common—for forehead lines
  • Drooping of the brows and upper eyelids
Less common—for glabellar lines
  • Drooping of the upper eyelid
  • facial pain
  • muscle weakness
  • partial or slight paralysis of the face
Less common—for lateral canthal lines
  • Swelling of the eyelids

Some side effects of onabotulinumtoxinA may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common—for blepharospasm
  • Blue or purplish bruise on the eyelids
  • drooping of the upper eyelids
  • irritation or watering of the eyes
  • sensitivity of the eyes to light
More common—for cervical dystonia More common—for chronic migraine
  • Neck pain
More common—for forehead lines
  • Headache
More common—for hyperhidrosis
  • Body aches or pain
  • chills
  • congestion
  • cough
  • diarrhea
  • dryness or soreness of the throat
  • fear
  • fever
  • general feeling of discomfort or illness
  • headache
  • heavy bleeding from the place where the shot was given
  • itching skin
  • joint pain
  • loss of appetite
  • nausea
  • nervousness
  • painful or difficult urination
  • runny nose
  • shivering
  • sweating
  • tender, swollen glands in the neck
  • trouble sleeping
  • trouble swallowing
  • voice changes
  • vomiting
More common—for strabismus
  • Drooping of the upper eyelid
  • eye pointing upward or downward instead of straight ahead
More common—for upper limb spasticity
  • Pain in the arms
Less common—for blepharospasm
  • Skin rash
  • swelling of the skin of the eyelid
Less common—for chronic migraine
  • Bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
  • blurred vision
  • body aches or pain
  • cough producing mucus
  • difficulty breathing
  • dizziness
  • drooping of the upper eyelid
  • headache
  • muscle aches and pains
  • nervousness
  • pounding in the ears
  • slow or fast heartbeat
  • tightness in the chest
Less common—for forehead lines
  • Skin tightness
Less common—for lower limb spasticity
  • Back pain
  • body aches or pain
  • chills
  • cough
  • difficulty in breathing
  • ear congestion
  • fever
  • headache
  • loss of voice
  • nasal congestion
  • sneezing
  • sore throat
  • unusual tiredness or weakness
Less common—for strabismus
  • Difficulty finding the location of objects
  • double vision
Less common—for upper limb spasticity
  • Cough producing mucus
  • difficulty breathing
  • muscle weakness
  • nausea
  • tightness in the chest
  • weakness

For Healthcare Professionals

Applies to onabotulinumtoxinA: injectable powder for injection


Common (1% to 10%): Constipation, nausea
Uncommon (0.1% to 1%): Dysphagia, oral dryness
Postmarketing reports: Abdominal pain, anorexia[Ref]

Nervous system

Common (1% to 10%): Headache, worsening migraine, facial paresis
Uncommon (0.1% to 1%): Vertigo
Frequency not reported: VII nerve disorder, new or recurrent seizures
Postmarketing reports: Brachial plexopathy
Nervous system side effects have included fatigue (2 to 3%), dizziness (2 to 10%), fever (2 to 10%), drowsiness (2 to 10%), and numbness (2 to 10%).[Ref]


Common (1% to 10%): Bronchitis, cough, rhinitis, dyspnea, pharyngitis[Ref]


Common (1% to 10%): Pain in extremity, muscle weakness, asthenia, back pain, hypertonia, stiffness, fall, gait disturbance, muscle spasm, neck pain, musculoskeletal stiffness, myalgia
Uncommon (0.1% to 1%): Jaw pain
Postmarketing reports: Denervation/muscle atrophy[Ref]


Common (1% to 10%): Hypertension
Frequency not reported: Arrhythmia, myocardial infarction (sometimes fatal)[Ref]


Common (1% to 10%): Injection site pain[Ref]


Common (1% to 10%): Flu syndrome, infection
Frequency not reported: Immunogenicity (formation of neutralizing antibodies to botulinum toxin type A which may reduce the effectiveness of therapy)[Ref]


Common (1% to 10%): Eyelid ptosis
Uncommon (0.1% to 1%): Dry eye, eyelid edema, eye infection, diplopia
Very rare (less than 0.01%): Corneal perforation
Frequency not reported: Superficial punctate keratitis, irritation, tearing, lagophthalmos, photophobia, ectropion, keratitis, diplopia, local swelling of the eyelid skin lasting for several days following eyelid injection, reduced blinking (from the injection of the orbicularis muscle which may lead to serious corneal exposure), persistent epithelial defect
Postmarketing reports: Visual disturbance[Ref]


Common (1% to 10%): Fatigue, dizziness, hypertonia, asthenia, speech disorder, fever, stiffness, numbness, non-axillary sweating, sweating
Very rare (less than 0.01%): Brachial plexopathy
Frequency not reported: Focal facial paralysis, syncope, exacerbation of myasthenia gravis
Postmarketing reports: Hypoacusis, hypoesthesia, malaise, paresthesia, peripheral neuropathy, radiculopathy, tinnitus[Ref]


Common (1% to 10%): Pruritus
Frequency not reported: Diffuse skin rash
Postmarketing reports: Alopecia (including madarosis), erythema multiforme, dermatitis psoriasiform, psoriasiform eruption[Ref]


Adverse reactions usually occur within the first week following injection of this drug and while generally transient, may have a duration of several months or longer. Localized pain, infection, inflammation, tenderness, swelling, erythema, and/or bleeding/bruising may be associated with the injection. Needle-related pain and/or anxiety may result in vasovagal responses (including e.g., syncope, hypotension), which may require appropriate medical therapy.[Ref]


Very common (10% or more): Urinary tract infection (26% in patients without diabetes and 31% in patients with diabetes), urinary retention (24%)
Common (1% to 10%): Dysuria, hematuria, bacteriuria, residual urine volume


Common (1% to 10%): Hemorrhage[Ref]


Common (1% to 10%): Anxiety[Ref]


1. "Product Information. Botox (onabotulinumtoxin A)." Allergan Inc, Irvine, CA.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.