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

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.
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. 


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.

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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.