MS exacerbations can involve symptoms like numbness, vision changes, and pain. But symptoms may vary. You may be able to prevent flare-ups by avoiding triggers like stress and infection, if possible.

In multiple sclerosis (MS), a flare-up is an episode of new symptoms or a worsening of old 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. With RRMS, symptoms can worsen during flare-ups and improve when the episodes resolve.

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

People experience flare-ups differently. Symptoms can vary each time one occurs.

Sometimes, they’re mild. Other times, symptoms can be so severe they make it difficult to function. There can be one symptom or more than one, depending on how the central nervous system (CNS) is affected and how many areas of the CNS are involved.

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

  • weakness in the legs or arms
  • blurred vision or eye pain due to optic neuritis, which is an inflammation of the optic nerve that affects and impairs vision
  • 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, MS can also lead to 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 only qualify as flare-ups if they:

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

Some of your symptoms can be present all the time and may worsen during a flare-up, such as fatigue, trouble concentrating, or bladder issues. And you might only have certain symptoms during your flare-ups.

People with RRMS experience flare-ups throughout the course of their disease.

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

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

There’s no way to completely cure MS, but disease-modifying therapies (DMTs) can help reduce or prevent flare-ups.

There also are ways to avoid the triggers, like stress and heat exposure, that may prompt them.


Living with MS is stressful, and it can help to talk with a professional therapist about how to reduce that stress so you can limit the impact of stress as a trigger.

According to a 2023 study based on self-reported data, stressful life events can increase the occurrence of MS flare-ups and the severity of the disease burden. Another study from 2022 noted an association between the COVID-19 pandemic, stress, depression, and MS relapses.

Keep in mind that stress is a fact of life. But you can take steps to reduce it. You can help lower your stress levels by:


According to older research from 2015, common viral infections, such as the flu or a cold, can trigger MS flare-ups. However, newer research from 2023 suggests that DMTs may prevent relapse from 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 people who are sick
  • wearing a mask when you are in a crowded place

Other risk factors

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

  • not taking DMTs
  • heat exposure
  • fatigue
  • serum levels of vitamin D
  • smoking

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

  • Surgery: According to the National MS Society, neither surgery nor anesthesia will bring about a flare-up.
  • Anesthesia: Anesthesia is generally considered safe for people who live with MS. People with advanced MS and respiratory problems have a higher risk of complications from anesthesia but not flare-ups. (However, complications are rare.)
  • 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 National MS Society has an entire page on its website dedicated to vaccines, including precautions to take in certain cases, including:

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

Discuss all medications with a doctor before making any changes.

About pseudo-exacerbations

Pseudoexacerbations are worsening MS symptoms that aren’t caused by new CNS inflammation that damages the myelin.

During a pseudo-exacerbation, symptoms that may have been present in the past will briefly worsen or reemerge. These symptoms are temporary. Potential causes include:

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

Once the reason for the pseudo-exacerbation is found and treated, the symptoms usually resolve within 1 day.

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To qualify as a flare-up, symptoms must last for at least 24 hours.

The duration of a flare-up can be different for each person and for each flare-up. Flare-ups may only last for a few days, but sometimes they can last for weeks or months.

Flare-ups can happen with little to no warning. However, you can take some steps to help prevent them. Maintaining overall health is important for everyone, but it’s especially necessary for people living with MS.

Much of what you can do involves preventing infections and supporting your overall health. To do that, eat a nutrient-rich and balanced diet.

If you smoke, try getting help to quit. Smoking increases the chances of chest infections and respiratory infections, which can bring on flare-ups. It’s also associated with worsening MS.

If you’re prescribed DMTs, be sure to take them as directed. Missing doses can cause problems. If you have concerns about your DMTs or any associated side effects, speak with a doctor to see what other options may be available. Do not stop taking a prescription medication without first talking with a doctor.

Make sure you have a support network and people who can help if you need it. Talk with your family and friends about how you’re feeling.

Some MS flare-ups may not need treatment. If symptom flare-ups occur but don’t affect your quality of life, doctors may recommend a wait-and-see approach. The issues may clear up on their own.

Some flare-ups cause more severe symptoms, such as extreme weakness, and require treatment. A 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 haven’t been effective.
  • Plasma exchange: This treatment replaces your blood plasma with new plasma. It’s used only for severe flare-ups when other treatments haven’t worked.

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

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

What does an MS flare-up feel like?

How an MS relapse feels can vary, depending on the part of the nervous system that is affected. It may include new symptoms and worsening of symptoms you already may have, such as fatigue or weakness.

How long do MS flare-ups usually last?

MS flare-ups last at least 24 hours but can last for weeks or months.

How do you calm an MS flare-up?

During a flare-up, doctors may recommend a specific treatment, such as corticosteroids, for the symptoms you’re experiencing. If symptoms do not disrupt your quality of life, they may recommend watching and waiting to see if they improve on their own.

For longer-lasting or severe flare-ups, they may recommend other treatments. After a flare-up is resolved, doctors may recommend treating lingering weakness with physical or occupational therapy.

What causes MS flare-ups?

Some triggers may make MS flare-ups more likely. These can include stress, hot temperatures, and infections.

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

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

Flare-ups may bring up emotional issues as well. Anxiety and depression may get worse. Talk with your doctor about whether therapy or similar mental health support is a good idea for you and for members of your family.

Different kinds of approaches may also be useful. This can include physical and occupational therapy, medication adjustments, and mental health therapy.