What are the side effects of Botox Cosmetic (onabotulinumtoxinA)?

Botox Cosmetic (onabotulinumtoxinA) can cause serious or life-threatening  muscle problems hours or weeks after the injection.  Botox Cosmetic may allow the spread of botulinum toxin and its effects to other areas in the body.
Contact your doctor immediately if you experience  muscle weakness, loss of bladder control, trouble swallowing, or trouble talking. Botox Cosmetic may also cause serious allergic reactions or anaphylaxis. Get immediate emergency help if you experience a rash; itching; a hoarse throat; difficulty swallowing or breathing; or swelling of the face, mouth, or hands.
Other severe side effects of this drug include bleeding at the site of injection, blurred or distorted vision, chest pain, difficulty swallowing, eyelid drooping or swelling, fainting, flu-like symptoms, irregular heartbeat, paralysis, seizures, weakness, or speech problems. Less-serious side effects include back pain, dizziness, sleepiness, dry eyes or mouth, pain in your face or neck, back pain, irritation at the injection site, runny nose, light sensitivity, weak muscles around the injection site, anxiety, mild fever or achiness, nausea, cough, or indigestion. See your doctor if these side effects persist or worry you.
Stuart A. Linder, MD
Plastic Surgery

The most common side effects of Botox include: anxiety, headaches, drowsiness, dry mouth, dry eyes, flu-like symptoms, cough, nausea, neck pain, redness, swelling or pain at the injection site, light sensitivity, sweating, and muscle weakness at the site of injection. The severe complications include: allergic reaction (rash, hives, shortness of breath,), bleeding at injection site, difficulty with swallowing or breathing, double vision, fever, chills, loss of bladder control, fainting, eyelid droop, persistent muscle weakness,  and worsened migraine headaches. 


The most common side effect of Botox is bruising. The package insert also mentions many other side effects that are still rare, but more likely for those using it in higher doses than what is used for cosmetic purposes, and also more likely when used for medical rather than aesthetic effects.

Continue Learning about Muscoloskeletal Agent

What should I know about leflunomide before taking it?
Donna Hill Howes, RNDonna Hill Howes, RN
Your doctor will need to do blood tests, check your liver function and blood pressure, and give you ...
More Answers
How long does it take to get pain relief from hyaluronic acid injections?
Dr. Vonda Wright, MDDr. Vonda Wright, MD
I never guarantee my patients that they're going to see any effect from hyaluronic acid (HA) injecti...
More Answers
How does leflunomide interact with other medications and foods?
Donna Hill Howes, RNDonna Hill Howes, RN
People taking leflunomide should avoid receiving live vaccines. If you are taking an immunosuppress...
More Answers
Is Synvisc a good alternative to joint replacement?
Keith Roach, MDKeith Roach, MD
Synvisc is not generally an alternative to joint replacement in people with very advanced knee osteo...
More Answers

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.