MS flare-ups may involve symptoms such as numbness, vision changes, and pain. But symptoms may vary. You may be able to prevent flare-ups by avoiding triggers such as stress and infection when possible.

In multiple sclerosis (MS), a flare-up is an episode of new symptoms or a worsening of existing symptoms. A flare-up may also be called:

  • an attack
  • a bout
  • an episode
  • an exacerbation
  • a relapse

Relapsing-remitting MS (RRMS) is the most common type of MS, according to the National Multiple Sclerosis Society (NMSS). In RRMS, symptoms may worsen during flare-ups and improve when flare-ups resolve, during periods known as remission.

Read on to learn more about MS flare-ups and how to treat and prevent them.

The type, severity, and number of symptoms that occur during an MS flare-up will vary for each person.

Each flare-up may show up differently, depending on how it affects your central nervous system (CNS) and how many areas of your CNS are involved.

A flare-up can involve new symptoms or worsening of existing symptoms. Symptoms of flare-ups may include:

  • weakness in your legs or arms
  • blurred vision or eye pain
  • balance problems or dizziness
  • severe fatigue
  • issues with memory or concentration
  • numbness, tingling, or a feeling of pins and needles
  • slurred speech or trouble swallowing
  • bladder issues, including incontinence or a frequent need to urinate

In serious cases, an MS flare-up may also cause temporary vision loss. This often occurs in just one eye and typically resolves when the flare-up is over.

It can be difficult to tell whether the symptoms you’re having are a flare-up or regular symptoms of your MS.

Symptoms qualify as a flare-up only if they:

  • occur at least 30 days after an earlier flare-up
  • last for 24 hours or longer
  • aren’t related to an infection or another medical cause
  • aren’t present between flare-ups

Some of your symptoms may be present at all times and worsen during a flare-up, or you might have certain symptoms only during your flare-ups.

If you have RRMS, you’ll experience flare-ups throughout the course of the disease.

Flare-ups are caused by inflammation in your CNS that damages myelin, a fatty substance that protects the portion of your cells called an axon.

Axons carry messages to other body parts, and the protective myelin helps speed up transmission of those messages. When the myelin is damaged due to inflammation, the messages are disrupted. This causes MS symptoms and flare-ups.

There’s no way to cure MS completely, but disease-modifying therapies (DMTs) can help reduce or prevent flare-ups. Avoiding triggers such as stress and heat exposure may also help.


Research suggests that stress may be a trigger for MS flare-ups.

A 2023 survey based on self-reported data found that stressful life events increased the occurrence of MS flare-ups and the severity of the disease burden.

And a 2022 study noted an association among the COVID-19 pandemic, stress, depression, and MS relapses.

Living with MS is stressful. You might find it helpful to talk with a professional therapist about how to reduce stress so you can limit the impact of stress as a trigger.

Other possible ways to help lower your stress levels include:

  • setting boundaries to avoid overextending yourself
  • exercising regularly
  • eating balanced meals
  • getting enough sleep
  • practicing meditation, chair yoga, or breathing exercises
  • talking with a therapist


According to a 2015 research review, common viral infections such as the flu and the common cold may trigger MS flare-ups.

However, a 2023 study suggests that DMTs may prevent relapse due to mild to severe infections.

While upper respiratory infections are common in the winter, you can take steps to reduce your risk, including:

  • getting a flu shot if your doctor recommends it
  • washing your hands often
  • avoiding close contact with people who are sick
  • wearing a mask when you’re in crowded places

Other risk factors

Other risk factors for flare-ups that researchers have identified include:

  • genetics
  • heat exposure
  • a high sodium diet
  • low levels of vitamin D
  • smoking

Some people may have concerns about other factors that they believe may trigger relapses, such as:

  • Surgery: According to the NMSS, neither surgery nor anesthesia will trigger a flare-up.
  • Anesthesia: Anesthesia is generally considered safe for people with MS, according to the NMSS. However, you may have a higher risk of complications from anesthesia (but not flare-ups) if you have advanced MS and respiratory problems.
  • Vaccines: Research has shown that vaccines don’t worsen MS. Studies have looked at all kinds of vaccines, from seasonal flu vaccines to hepatitis B and even the current COVID-19 vaccines.

The NMSS has a website page dedicated to vaccines, which mentions precautions to take in certain cases, such as:

  • not getting a vaccine while you’re experiencing a flare-up
  • avoiding live-virus vaccines if you’re taking certain kinds of medication

It’s important to discuss all medications with your doctor before making any changes.

About pseudo-exacerbations

Pseudo-exacerbations are times when MS symptoms worsen for less than 24 hours. This is sometimes called the Uhthoff sign or syndrome.

The exact cause of MS pseudo-exacerbations isn’t known, but researchers believe they may be due to changes within your CNS when your body temperature is elevated. Other potential causes include:

  • an environment that’s too warm
  • an illness or infection, especially a urinary tract infection (UTI)
  • depression and anxiety, which are often brought on by stress
  • exhaustion
  • exercise

During a pseudo-exacerbation, symptoms that may have been present in the past will briefly worsen or reemerge. Symptoms usually resolve within 1 day once the underlying cause is found and treated.

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Symptoms must last for at least 24 hours to qualify as a flare-up.

The duration of a flare-up may vary for each person and each flare-up. For example, some flare-ups may last only a few days, but others could last for weeks or months.

Flare-ups can happen with little to no warning, but you can take some steps to help prevent them, such as:

If you have a treatment plan, it’s important to follow it as directed by your doctor. This may include taking DMTs if your doctor has prescribed them. Missing doses can cause problems.

If you have concerns about your DMTs or any associated side effects, you can talk with your doctor about other options. Do not stop taking a prescription medication without consulting your doctor.

Establishing a support network of family, friends, and healthcare professionals may also help you manage triggers such as stress.

Treatment for MS flare-ups will depend on several factors, such as the type and severity of your symptoms.

For mild symptom flare-ups that don’t affect your quality of life, you might be able to take a wait-and-see approach, and the symptoms may clear up on their own.

However, flare-ups that cause more severe symptoms, such as extreme weakness, may require treatment. Your doctor may recommend:

  • Corticosteroids: These medications can help bring down inflammation in the short term.
  • H.P. Acthar gel: This injectable medication is generally used only when corticosteroids have not been effective.
  • Plasma exchange: This treatment replaces your blood plasma with new plasma. It’s used only for severe flare-ups when other treatments have not worked.

If a flare-up is very severe, your doctor may suggest restorative rehabilitation as you start to regain strength. This treatment may involve:

  • physical therapy
  • occupational therapy
  • treatment for difficulties with speech, swallowing, or thinking

Since flare-ups can be different for each person, recovery may be different as well. Some tips that may help include:

  • temporarily reducing your activity level
  • taking time off from work, if possible and necessary
  • asking for help with household tasks, if necessary
  • getting professional at-home help from a nurse

Flare-ups may bring up emotional issues as well. If you typically experience anxiety and depression, they may get worse. You can talk with your doctor about whether therapy or similar mental health support is a good idea for you and for members of your family.

Other approaches, such as physical and occupational therapy and medication adjustments, may also be helpful.

What does an MS flare-up feel like?

How an MS relapse feels can vary, depending on the part of your nervous system the disease affects. A flare-up may involve new symptoms and worsening of existing symptoms such as fatigue or weakness.

How do you recover from an MS flare-up?

Recovery will depend on the severity and type of symptoms you experience. Mild symptoms such as fatigue may get better on their own. More serious symptoms such as vision loss, dizziness, or balance issues may require medical treatment like corticosteroids, H.P. Acthar gel, or plasma exchange.

Should you rest during an MS flare-up?

If you experience a pseudo-exacerbation, rest may help you fully recover. Rest may also help you recover during longer flare-ups, as fatigue is a common symptom. But it’s also important to get regular physical activity.

Talk with your doctor if you’re unsure how much rest you should get. They can develop a resting plan based on your current health condition.

What foods cause MS flare-ups?

There’s no single diet for people with MS. Some foods may worsen your symptoms but may not affect someone else, and vice versa. A 2018 review suggests that high fat and high sodium diets may play a role in MS. However, the authors note that more research is needed to explore the link between diet and MS.

MS flare-ups are periods when you experience new or worsening symptoms. Flare-ups typically last for at least 24 hours.

You can manage flare-ups by resting, avoiding triggers, and eating a well-balanced diet, among other methods.

But if your flare-ups affect your day-to-day activities, talk with your doctor. They can help develop a treatment plan that’s right for you.