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Botox (onabot) is most commonly thought of as a cosmetic treatment that can smooth fine facial wrinkles. However, the medicine received FDA approval for the treatment of chronic migraine in October 2010. Chronic migraine is defined as headaches that occur on 15 or more days per month for more than 3 months. According to this definition, the headaches have to include migraine symptoms on 8 of those days.1

Botox is an injectable form of botulinum toxin called onabotulinumtoxin A. It is currently the only FDA-approved medicine for preventing chronic migraine. People with the most frequent migraine appear to see the best results with Botox treatments.2 In clinical studies, Botox reduced headache days by 50% over 6 months for chronic migraine sufferers.3

Botox is generally well tolerated by patients and does not result in problems with thinking, mood, or weight gain, which can be issues with other preventive medications.4

What are the ingredients in Botox?

The active ingredient in Botox is onabotulinumtoxin A.

How does Botox work?

Botox works by binding to certain areas, known as receptors, on nerves and muscle fibers. This blocks the release of specific brain chemicals, including acetylcholine. This, in turn, blocks muscle activity.5 It is not completely known how Botox reduces headache pain and stiffness. A potential reason might be that Botox blocks nerves that send pain messages to the brain and relaxes muscles so they are less sensitive to pain.

What are the possible side effects of Botox?

The most common side effects of Botox have been:

  • Neck pain
  • Temporary increase in headache days
  • Temporary droopy eyelids or eyebrows6

Other side effects include:

  • Dry mouth
  • Discomfort or pain at injection site
  • Tiredness
  • Eye problems, like double vision, blurred vision, or decreased eyesight
  • Swelling of the eyelids
  • Dry eyes7

This is not an exhaustive list of all potential side effects of Botox. For more information, consult your doctor or healthcare provider. If you notice any new or worsening side effects, contact your doctor or healthcare provider immediately.

Things to note about Botox

In rare circumstances, the paralyzing effect of Botox can spread to other areas of the body and can cause general weakness, double vision, difficulty swallowing, voice and speech disorders, loss of bladder control, and difficulty breathing. This has not happened when the medicine is used at approved doses for treatment of chronic migraine.

You should not take this medication if you are allergic to it, have a skin infection at the injection site, are being treated for urinary incontinence or cannot empty your bladder and have a urinary tract infection (UTI). This medication is not approved for children.

Seek immediate medical attention if you experience problems breathing or swallowing, or if you have signs of allergy, including swelling in the face, throat, lips, or tongue.

Before taking Botox, tell your doctor if you:

  • Have a disease that affects your muscles and nerves (such as ALS, or Lou Gehrig’s disease)
  • Have allergies or side effects from any botulinum toxin products
  • Have or have had a breathing problem, such as asthma or emphysema
  • Have or have had problems swallowing
  • Have or have had bleeding problems
  • Have plans to have surgery or have had surgery on your face
  • Have weakness of your forehead muscles, such as trouble raising your eyebrows or have droopy eyelids
  • Have symptoms of a urinary tract infection (UTI)
  • Are pregnant or plan to become pregnant
  • Are breastfeeding or plan to breastfeed8

Botox dosing information

Botox is available in injectable form and is administered at a doctor’s office. Botox and Botox Cosmetic (the form of Botox given for reducing facial wrinkles) both contain the same ingredients but have different approved uses and labeling.

When given for chronic migraine, Botox is diluted and a series of 31 injections are given across 7 specific regions on both the left and right sides of the head and neck. It is recommended that this treatment is repeated every 12 weeks. Each procedure takes about 15 minutes.

Many insurance companies require that people with chronic migraine try other preventive medications first before they will cover Botox for migraine prevention.8

Written by: Sara Finkelstein | Last reviewed: August 2019
  1. Chronic Migraine. American Migraine Foundation. Published November 13, 2016. Accessed May 4, 2018.
  2. Botox for Migraine. American Migraine Foundation. Published June 14, 2017. Accessed May 4, 2018.
  3. Mark Whetherall. The diagnosis and treatment of chronic migraine. Ther Adv Chronic Dis. 2015 May; 6(3): 115–123. Available at Accessed May 4, 2018.
  4. Prevention of Migraine. American Migraine Foundation. Published September 3, 2014. Accessed May 4, 2018.
  5. Prescribing Information. Allergan Pharmaceuticals. Published October 2017. Accessed May 4, 2018.
  6. Treatment of Chronic Migraine using Botox. American Migraine Foundation. Published April 6, 2018. Accessed May 4, 2018.
  7. Don’t Lie Down Stand Up to Chronic Migraine. Allergan Pharmaceuticals. Accessed May 4, 2018.
  8. Medication Guide Botox. Allergan Pharmaceuticals. Published October 2017. Accessed May 4, 2018.