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Botox Side Effects

Generic Name: onabotulinumtoxinA

Note: This page contains information about the side effects of onabotulinumtoxinA. Some of the dosage forms included on this document may not apply to the brand name Botox.

Not all side effects for Botox may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to onabotulinumtoxinA: powder for solution

In addition to its needed effects, some unwanted effects may be caused by onabotulinumtoxinA (the active ingredient contained in Botox). In the event that any of these side effects do occur, they may require medical attention.

If any of the following side effects occur while taking onabotulinumtoxinA, check with your doctor or nurse immediately:

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 or rare—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 lateral canthal lines
  • Swelling of the eyelids

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

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
  • Body aches or pain
  • chills
  • cough, fever, sneezing, or sore throat
  • ear congestion
  • headache
  • loss of voice
  • nasal congestion
  • neck pain
  • runny nose
  • unusual tiredness or weakness
More common—for chronic migraine
  • Neck pain
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 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
  • Muscle weakness
  • pain in the arms
Less common or rare—for blepharospasm
  • Skin rash
  • swelling of the eyelid skin
Less common or rare—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
  • wheezing
Less common or rare—for strabismus
  • Difficulty finding the location of objects
  • double vision
Less common—for upper limb spasticity
  • Cough producing mucus
  • difficulty breathing
  • nausea
  • shortness of breath
  • tightness in the chest
  • weakness
  • wheezing

For Healthcare Professionals

Applies to onabotulinumtoxinA: injectable powder for injection


Gastrointestinal side effects have included nausea (2 to 3%), oral dryness (2 to 10%), and dysphagia (2 to 10%).[Ref]

Nervous system

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%). New or recurrent seizures have been reported, usually in patients who are predisposed to experiencing these events. The exact relationship of these events to the injection of onabotulinumtoxinA (the active ingredient contained in Botox) has not been established.[Ref]


Respiratory side effects have included bronchitis (2 to 3%), increased cough (2 to 10%), rhinitis (2 to 10%), and dyspnea (2 to 10%).[Ref]


Musculoskeletal side effects have included pain in extremity (6%), muscle weakness (4%), asthenia (2 to 10%), back pain (2 to 10%), hypertonia (2 to 10%), and stiffness (2 to 10%).[Ref]


Cardiovascular side effects have included arrhythmia and myocardial infarction, some with fatal outcomes. Some patients had risk factors including cardiovascular disease. The exact relationship of these events to the injection of onabotulinumtoxinA (the active ingredient contained in Botox) has not been established.[Ref]


Local side effects have included soreness at injection site (2 to 10%).[Ref]


Immunologic side effects have included flu syndrome (2 to 10%).[Ref]


Ocular side effects have included diplopia (2 to 10%) and ptosis (2 to 10%). Other events reported in prior clinical studies in decreasing order of incidence include: irritation, tearing, lagophthalmos, photophobia, ectropion, keratitis, diplopia, entropion, diffuse skin rash, and local swelling of the eyelid skin lasting for several days following eyelid injection.[Ref]

In two cases of VII nerve disorder, reduced blinking from onabotulinumtoxinA injection of the orbicularis muscle led to serious corneal exposure, persistent epithelial defect, corneal ulceration and a case of corneal perforation. Focal facial paralysis, syncope, and exacerbation of myasthenia gravis have also been reported after treatment of blepharospasm.

Extraocular muscles adjacent to the injection site can be affected, causing vertical deviation, especially with higher doses of onabotulinumtoxinA. The incidence rates of these adverse effects in 2058 adults who received a total of 3650 injections for horizontal strabismus was 17%.

The incidence of ptosis has been reported to be dependent on the location of the injected muscles, 1% after inferior rectus injections, 16% after horizontal rectus injections and 38% after superior rectus injections.

In a series of 5587 injections, retrobulbar hemorrhage occurred in 0.3% of cases.[Ref]


Other side effects have included speech disorder (2 to 10%). Other side effects reported postmarketing have included abdominal pain, anorexia, brachial plexopathy, diarrhea, facial palsy, facial paresis, hyperhidrosis, hypoacusis, hypoesthesia, localized numbness, malaise, myalgia, paresthesia, pyrexia, radiculopathy, skin rash (including erythema multiforme, and psoriasiform eruption), tinnitus, vertigo, visual disturbances, and vomiting.[Ref]

Side effects occurring most commonly in patients with cervical dystonia have included dysphagia (19%), upper respiratory infection (12%), neck pain (11%), and headache (11%). One female patient treated for cervical dystonia developed brachial plexopathy 2 days after injection of 120 Units of onabotulinumtoxinA.[Ref]

Other side effects occurring after treatment for axillary hyperhidrosis at a frequency of 3 to 10% have included injection site pain and hemorrhage, non-axillary sweating, infection, pharyngitis, flu syndrome, headache, fever, neck or back pain, pruritus, and anxiety.[Ref]


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

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.