Side Effects of Botox: What to Know

Medically Reviewed By Heather Bruce, PharmD

Botox has a boxed warning for the spreading of Botox’s toxin effect. This is a serious warning from the Food and Drug Administration (FDA).

After it’s injected into your body, Botox may spread outside of the areas where you received the injection. This can lead to symptoms that are similar to botulism poisoning.

For details, see the “ Botox: Side effects explained” section below.

Botox: Introduction

Botox is a brand-name prescription drug. It’s a type of drug called a neurotoxin. It contains the active drug onabotulinumtoxinA.

Botox comes as a powder inside vials. It’s mixed with liquid to form a solution, which is injected by a healthcare professional. In most cases, Botox is given as an intramuscular injection. However, the type of injection and the injection site vary depending on the condition Botox is being used to treat.

Botox is approved by the Food and Drug Administration (FDA) for the following purposes in certain situations to:

Similar to other drugs, Botox may cause side effects. Read below for information about possible side effects, including common, mild, and serious ones.

This article focuses on Botox that’s used for medical purposes. For a general overview of Botox and its medical uses, see this article. To learn more about Botox that’s used for cosmetic purposes, read this article.

If you’d like to use Botox, search here to find a healthcare professional who might prescribe it.

Botox: More common side effects

Some of Botox’s side effects may be more common than others. These side effects may last only a few days to weeks. However, some side effects may last longer or become severe or bothersome. Tell your doctor or pharmacist if you have concerns about any side effects with Botox.

Some of the more common side effects of Botox that occurred during clinical studies are listed below. These side effects can vary depending on the condition Botox is being used to treat. For example, people using Botox for migraine headaches might have different side effects than people using Botox for bladder problems.

Condition being treated More common side effects
Migraine headache headache*
neck pain
Bladder problems urinary tract infection (UTI)
urinary retention (inability to empty your bladder completely)
pain with urination
Spasticity arm or leg pain
Cervical dystonia (involuntary muscle spasms in the neck) •headache*
trouble swallowing
upper respiratory infection, such as the common cold
flu-like symptoms, such as body aches and fever
back or neck pain
Excessive underarm sweating •excessing sweating in places other than your underarms
•flu-like symptoms, such as body aches and fever
•injection site side effects, such as pain and bruising*
Eye twitching or crossed eyes •mild eye problems, such as eye drooping*

* For more information about this side effect, see “Botox: Side effects explained” below.

Botox: Mild side effects

Botox can cause mild side effects, some of which are listed below. However, this list doesn’t include all possible mild side effects. To learn more about Botox’s side effects, view the drug’s prescribing information.

These side effects can vary depending on the condition Botox is being used to treat.

Botox’s mild side effects include:

The side effects listed above may last only a few days to weeks. However, some side effects may last longer or become severe or bothersome. Tell your doctor or pharmacist if you have concerns about side effects with Botox.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while receiving Botox and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Botox: Side effects explained” below.

Botox: Serious side effects

It’s possible to have serious side effects with Botox. Some serious side effects are listed below, but this list may not include all possibilities. To learn more about Botox’s side effects, view the drug’s prescribing information.

Call your doctor right away if you have serious side effects with Botox. However, if you think you’re having a medical emergency or life threatening side effects, call 911 or your local emergency number.

Serious side effects of Botox and their possible symptoms include:

  • Overreaction of the nervous system, which may lead to a sudden increase in blood pressure. Symptoms can include:
    • severe headache
    • sweating
    • dizziness
    • flushing
  • Urinary retention (inability to empty your bladder completely). Symptoms can include
    • trouble starting to urinate
    • weak urine flow
    • frequent urge to urinate
  • Trouble swallowing. Symptoms can include:
    • choking
    • painful swallowing
    • regurgitation (spitting up) of food or drink
  • Allergic reaction.*†
  • Spreading of Botox’s toxin effect.‡
  • Severe eye problems.†

* An allergic reaction is possible after receiving Botox. However, it’s not clear whether this side effect occurred in clinical studies.
† For more information about this side effect, see “Botox: Side effects explained” below.
Botox has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Botox: Side effects explained” section below.

Botox: Side effects in children

Botox is approved to treat certain bladder, muscle, and eye problems in children.

In clinical studies, most of Botox’s side effects in children were the same as those in adults. However, white blood cells were present in the urine of children who received Botox injections.

Also, children with bladder problems may have a higher risk of certain side effects with Botox. Examples include:

Additionally, children with arm spasticity may have a higher risk of upper respiratory infections, such as the common cold. (Spasticity is a condition that causes muscle stiffness and spasms.)

If you’re concerned about a child’s risk of side effects with Botox, talk with their doctor.

Botox: Side effects explained

Here’s detailed information about some of Botox’s side effects.

Spreading of Botox’s toxin effect

Botox has a boxed warning for the possible spreading of its toxin effect. This is a serious warning from the Food and Drug Administration (FDA). A boxed warning is the strongest warning required by the FDA. Boxed warnings alert doctors and patients about drug effects that may be dangerous.

After it’s injected into your body, Botox may spread outside of the area where you received the injection. This can lead to symptoms that are similar to botulism poisoning. These symptoms can include:

These symptoms could occur within hours of receiving a Botox injection. However, there have been reports of this side effect happening several weeks after the drug was injected.

The spreading of Botox’s toxin effect is rare. Although it wasn’t reported in clinical studies of the drug, this side effect has been reported since Botox became available for use.

People who already have trouble breathing or swallowing may have a higher risk of this side effect.

What to do

If you have any of the symptoms listed above after getting a Botox injection, tell your doctor right away. However, if your symptoms seem life threatening, call 911 or your local emergency number.

Eye problems, such as eye drooping

Botox may also cause certain eye problems. In clinical studies, these side effects were more common when Botox was used to treat eye problems than when it was used for other conditions.

Examples of mild eye problems that can happen with Botox include:

In rare cases, Botox can cause more serious eye problems, such as ulcers (sores) on the cornea. Symptoms include light sensitivity and a sensation of having something in your eye.

Keep in mind that double vision and blurry vision can be symptoms of a more severe side effect of Botox. For details, see “Spreading of Botox’s toxin effect” above.

What to do

If you have symptoms of eye problems after receiving a Botox injection, talk with your doctor. They’ll likely check to make sure you aren’t having a more severe eye problem.

Injection site side effects, such as bruising

Botox may cause injection site side effects. These can happen around the area where Botox is injected.

In clinical studies, injection site side effects were most common when Botox was used to treat excessive underarm sweating. However, it’s possible to have injection site side effects when the drug is used to treat any condition.

Examples of these side effects include:

What to do

If you have bothersome injection site side effects after getting Botox injections, talk with your doctor. They can suggest ways to ease your symptoms. For example, they may suggest that you place a cold compress on the injection site to reduce swelling.

Headache

Headache may occur with Botox.

In clinical studies, this side effect was commonly reported when Botox was used to:

With headache, you have pain around your face, neck, or head. The duration, location, and severity of these symptoms can vary from person to person.

What to do

If you have headaches that bother you after getting a Botox injection, talk with your doctor. They can suggest ways to manage this side effect. For example, your doctor may recommend over-the-counter medications such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). They may also reduce your Botox dose or recommend a treatment other than Botox for your condition.

Nausea

Botox may also cause nausea. This was one of the most common side effects in clinical studies of Botox for treating spasticity. This was a rare side effect in studies of Botox for cervical dystonia (involuntary muscle spasms in the neck).

What to do

If you have bothersome nausea with Botox, talk with your doctor. They can suggest ways to ease your symptoms. For example, they may recommend over-the-counter medications that help lessen nausea. Examples include bismuth subsalicylate (Pepto-Bismol) and meclizine (Bonine).

Allergic reaction

As with most drugs, some people can have an allergic reaction after receiving Botox. A more severe allergic reaction is rare but possible.

This side effect wasn’t reported in clinical studies of Botox. However, allergic reaction has been reported since the drug became available to use.

Possible symptoms of mild and serious allergic reactions are listed in the table below.

Mild allergic reaction symptoms Serious allergic reaction symptoms
• itching trouble breathing
rash • swelling in your throat or mouth
flushing • swelling under your skin, possibly in your hands, feet, lips, or eyelids

If you have an allergic reaction to Botox, call your doctor right away. This is important to do because the reaction could become severe.

However, if you’re having a medical emergency or your symptoms feel life threatening, call 911 or a local emergency number.

Botox: Common questions about side effects

Here are some common questions about the drug’s side effects and answers to them. Talk with your doctor if you have other questions about this drug.

Does Botox have long-term side effects?

In rare cases, Botox may cause long-term side effects. This includes side effects that occur several weeks after an injection and ones that lead to long-term complications.

For example, Botox has a boxed warning about the spreading of the drug’s toxin effect. This is a serious warning from the Food and Drug Administration (FDA). There have been reports of this side effect happening several weeks after the drug was injected. For details, see the “Botox: Side effects explained” section above.

Additionally, when used to treat certain conditions, Botox may cause severe eye problems. This includes ulcers (sores) on the cornea. Without treatment, ulcers on the cornea can lead to long-term vision loss. For more information, see the “Botox: Side effects explained” section above.

If you’re concerned about long-term side effects with Botox, talk with your doctor. They can tell you about your risk of side effects with Botox and advise if it’s a safe treatment option for you.

Are there risks or dangers to using Botox?

As with all medications, using Botox comes with certain risks. In rare cases, using Botox may lead to negative effects.

For example, Botox has a boxed warning about the spreading of the drug’s toxin effect. This is a serious warning from the FDA. For details about this and other side effects of the drug, see the “Botox: Side effects explained” section above.

Your doctor can tell you about the risks and benefits of Botox. They’ll also determine whether Botox is safe for you to use.

Will Botox cause neurological side effects, such as brain effects?

Probably not. Neurological side effects weren’t reported in clinical studies of Botox. (“Neurological” describes conditions that affect the brain, spinal cord, or other parts of the nervous system.)

If you’re concerned about neurological side effects with Botox, talk with your doctor.

Botox: Precautions

Below are precautions related to Botox.

Boxed warning: Spreading of Botox’s toxin effect

This drug has a boxed warning for the spreading of Botox’s toxin effect. This is a serious warning from the Food and Drug Administration (FDA).

After it’s injected into your body, Botox may spread outside of the areas where you received the injection. This can lead to symptoms that are similar to botulism poisoning.

For details, see the “Botox: Side effects explained” section above.

Other precautions

Be sure to talk with your doctor about your health history before you receive Botox. This drug may not be the right treatment option for you if you have certain medical conditions or other factors that affect your health.

Some conditions and factors to consider include those described below.

  • Neuromuscular disorders. Before getting Botox injections, tell your doctor if you have a neuromuscular disorder, such as myasthenia gravis. These conditions could increase your risk of certain side effects with Botox. Examples include eye problems and trouble swallowing. If you have a neuromuscular disorder, your doctor will advise if it’s safe to get Botox injections.
  • Trouble breathing or swallowing. If you have trouble breathing or swallowing, you may have a higher risk of the spreading of Botox’s toxin effect.* Be sure to tell your doctor if you have any breathing or swallowing conditions before using Botox.
  • Trouble emptying your bladder. Doctors may not prescribe Botox for bladder problems in people who already have trouble emptying their bladder. People with this condition may have an increased risk of urinary retention (inability to empty the bladder completely) with Botox. However, doctors could prescribe Botox for people who have this condition and empty their bladder with a catheter. If you have trouble emptying your bladder, your doctor will advise if it’s safe to use Botox.
  • Infections around a Botox injection site. Before getting a Botox injection, tell your doctor if you have an infection around the planned injection site. They’ll likely postpone your injection until the infection heals.
  • Allergic reaction. If you’ve had an allergic reaction to Botox or any of its ingredients, your doctor will likely not prescribe Botox. Ask your doctor what other medications may be better options for you.
  • Planned surgery. Certain medications that are used during surgery could increase your risk of side effects with Botox. If you’re planning to have surgery, be sure to tell your doctor. They may adjust your Botox injection schedule to avoid giving you Botox around the time of your surgery.

* Botox has a boxed warning for this side effect. This is a serious warning from the FDA. For details, see the “Botox: Side effects explained” section above.

Consuming alcohol during Botox treatment

There aren’t any known interactions between alcohol and Botox. However, alcohol may worsen certain side effects of Botox. Examples include headache and nausea.

If you drink alcohol, talk with your doctor about the amount that’s safe for you to drink while receiving Botox.

Pregnancy and breastfeeding during Botox treatment

It isn’t known if Botox is safe to use while pregnant or breastfeeding. If you have questions about getting Botox injections during these times, talk with your doctor.

Botox: What to discuss with your doctor

Talk with your doctor or pharmacist to find out more information about Botox. If you have questions about the drug’s side effects, your pharmacist or healthcare professional can help answer them for you.

In addition to discussing Botox with your doctor, you may find the following articles helpful in learning more.

Disclaimer: Healthgrades 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.

Medical Reviewer: Heather Bruce, PharmD
Last Review Date: 2022 Apr 10
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.