Botox (onabotulinumtoxinA) is used for cosmetic and medical purposes, including migraine headache prevention. While Botox is generally safe, some people may experience side effects, including headache.

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Both Botox and Botox Cosmetic are brand-name prescription injections that contain the active ingredient onabotulinumtoxinA. When injected in small amounts, Botox temporarily paralyzes muscles. This can relieve muscle spasms that cause migraine headaches or other conditions. It can also reduce the appearance of facial lines.

Keep reading to learn about headache as a side effect of Botox.

Boxed warning: Spread of toxin effects

Botox has a boxed warning for the spread of toxin effects. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

In some cases, Botox’s effects may spread away from the site where the drug is injected. This side effect occurs when Botox’s active ingredient, onabotulinumtoxinA, spreads away from the injection site and causes botulism (muscle paralysis due to botulinum toxin). The following symptoms may occur:

• fatigue
• muscle weakness all over your body
• drooping eyelids
• double vision
• loss of bladder control
• hoarse voice
• difficulty speaking
• difficulty breathing
• difficulty swallowing

These symptoms can occur hours, days, or weeks after you’ve had a Botox injection. Be sure to tell your doctor if you develop any symptoms of botulism, even if they do not occur right after you receive a Botox injection.

Breathing and swallowing problems caused by Botox can sometimes be life threatening. The risk of these problems is higher in people who already have problems with breathing or swallowing.

If you have difficulty breathing, swallowing, or speaking after having a Botox injection, contact your doctor right away. But if your symptoms feel life threatening, call 911 or your local emergency number.

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Headaches are a common side effect of Botox. In clinical trials, headache was common in people taking Botox for chronic migraine or for cervical dystonia (involuntary muscle spasms in the neck).

It isn’t fully known why headaches may happen with Botox. But below are a few reasons why they may occur:

  • Injection site reaction: Botox is injected in several sites, including the forehead, above the eyebrows, the temple, and the neck. It’s possible to experience injection site reactions such as pain, infection, inflammation, tenderness, and swelling in these areas. These reactions may cause headaches.
  • Muscle tension: Botox is typically injected into muscle. This type of injection and Botox’s effects on the muscles may temporarily cause muscle tension or soreness, which can lead to a headache.
  • Nerve irritation: The needle used for Botox injections may irritate nerves near the injection site, triggering a headache.
  • Allergic reaction: Your immune system may recognize Botox as a foreign substance, resulting in an immune response and an allergic reaction. This may lead to headaches.
  • Response to the drug: Some people are more sensitive to Botox or to injections in general. As a result, they may have a higher risk of experiencing headaches.

The type of headache you experience after Botox can vary. It may feel like:

  • a sinus headache, with head and nasal pressure
  • a tension headache, with tightness around your head
  • a migraine headache, with intense throbbing pain
  • pain around the injection site that radiates to your head

Side effects of Botox are typically mild and temporary. In clinical trials, side effects started within a week of the injection and eventually went away. However, some side effects lasted several months or longer. Be sure to talk with your doctor if you have constant headaches or if they become bothersome.

Keep in mind that Botox will wear off eventually and you’ll likely need more doses to continue treatment. So if you usually develop a headache after your injection, it may occur every time you get Botox treatment. Typically, your doctor will wait at least 12 weeks between treatment sessions.

To help relieve headaches after Botox, your doctor may recommend taking over-the-counter pain relievers such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin).

You may benefit from getting plenty of rest and drinking water, as dehydration can worsen headaches. Gentle massages or warm or cold compresses on your forehead can also help relieve pain and tension.

When to see your doctor

While most headaches after Botox are mild and go away on their own, it’s important to contact your doctor if your headache is severe or doesn’t ease. If you experience other symptoms, such as numbness, dizziness, or vision changes, or if you have a fever or a stiff neck, contact your doctor. These could be signs of more serious side effects of Botox.

If you’re receiving Botox to help prevent migraine headaches and you’re still having them, talk with your doctor. They may be able to recommend options other than Botox, such as topiramate (Topamax).

To help prevent headaches with Botox, be sure to tell your doctor your entire medical history before starting treatment. Let them know if you have a history of headaches or injection site reactions. To help avoid interactions with Botox, you should also tell them about any medications or supplements you take.

Before your Botox injection, it may be helpful to avoid alcohol and stay hydrated. After your injection, be sure to follow any Botox aftercare instructions that your doctor provides.

Headaches after Botox are usually temporary and manageable. However, if they do not go away or if you’re unable to tolerate them, talk with your doctor. They can help you manage headaches or recommend a different treatment for your condition.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.