Multiple sclerosis (MS) is a condition that results in inflammation of the central nervous system (CNS). People with MS sometimes experience exacerbations, which is when old symptoms worsen or new ones develop.

In MS, the body attacks the myelin sheath, which is the protective covering around the nerve fibers, disrupting communications from the brain. This can lead to various symptoms, ranging from muscle weakness to changes in thinking and memory.

An exacerbation — also known as a relapse, a flare-up, or an attack — is a period when disease activity increases. Exacerbations can last from several days to several months, although the latter is rare.

Experts do not know precisely what causes exacerbations. However, there may be a link between high levels of inflammation and structural changes in the brain. Some triggers, such as an infection, may increase the risk.

In this article, we look at what triggers MS exacerbations, how they affect people with different types of MS, and how to recognize and manage them.

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Medical Illustration by Bailey Mariner

Possible triggers of an MS exacerbation include:

Below, we discuss each of these potential triggers in detail.

Infection

Viral, bacterial, and fungal infections may trigger an MS exacerbation.

People with MS may wish to take steps to reduce their risk of infection, such as washing their hands frequently and speaking with a doctor about appropriate vaccinations.

Vaccinations

It is unclear whether vaccinations worsen the symptoms of MS or not. There are concerns that some live vaccines, such as the shingles or yellow fever vaccines, may have this effect.

However, an infection may be more likely than a vaccine to trigger an exacerbation. Anyone with concerns should discuss vaccination with a healthcare professional.

Can I have a COVID-19 vaccination with MS?

Childbirth

People with MS usually find that disease activity decreases during pregnancy.

However, up to 30% of people may experience exacerbations in the first 3 months after delivery. This is more likely if a relapse occurred during pregnancy or just before or around the time of conception.

Here, learn more about how MS affects pregnancy.

Stress

Stress may trigger MS exacerbations, although research has not yet confirmed this.

Vitamin D deficiency

Low levels of vitamin D can contribute to the risk of MS exacerbations. A person with MS should regularly monitor their vitamin D levels and boost them when appropriate.

Sleep problems

A small 2017 study suggests that sleep disturbances or lack of sleep may trigger a relapse in people with MS.

It is important to recognize when a relapse occurs, as prompt treatment can help reduce the impact of an exacerbation on a person’s ability to function in daily life.

A new MS exacerbation would have the following criteria:

  • Previous symptoms have reappeared or worsened, or new symptoms have emerged.
  • Symptoms have persisted for longer than 24 hours. More commonly, symptoms last for weeks or even months.
  • A period of 30 days must have passed since the start of the previous relapse.
  • A healthcare professional has ruled out other possible causes of symptoms, such as heat or an underlying infection.

What is not an exacerbation?

A person may also experience temporary flare-ups of symptoms that typically resolve without active treatment and do not involve additional damage to the myelin sheath. These do not qualify as exacerbations. Health experts call them pseudoexacerbations.

Examples include:

  • symptoms getting worse in high or low temperatures that resolve after moderate temperature resumes
  • daily fluctuations, for example, due to fatigue or a peak in stress or activity levels
  • a mild infection that makes symptoms worse without triggering a full relapse, such as a stomach bug

Common relapse symptoms

The most common symptoms of MS that occur during a relapse include:

Some relapses are mild and do not have a severe impact on daily functioning. Others will require hospitalization.

Common symptoms of MS can include:

During exacerbations, one or more of these may appear or worsen. They may then improve or disappear during a remission, or they can become permanent.

Exacerbations work differently in each type of MS.

Clinically isolated syndrome

Clinically isolated syndrome (CIS) is the first episode of CNS inflammation and damage to the protective coating of nerve cells. It produces symptoms that last for at least 24 hours.

CIS usually develops in young adults and affects the spinal cord, brain stem, or optic nerve.

Not everyone who experiences CIS will develop MS. Some people have no further symptoms.

However, some individuals who experience CIS go on to receive a diagnosis of MS. Those people usually have specific brain lesions that show up in imaging tests.

If tests show that a person with CIS has those brain lesions, there is a 60–80% likelihood of developing MS within a few years. For this reason, a doctor may recommend treatment to help prevent further symptoms from occurring.

Relapsing-remitting MS

People with a diagnosis of relapsing-remitting MS (RRMS) will often experience exacerbations in the form of a relapse that has a clear start and endpoint.

Sometimes, all symptoms improve, but specific symptoms may persist and become permanent.

During remission, MS will not often progress, and there will be no exacerbations. A person may have no symptoms for several months or years. When a relapse occurs, MRI results may show new brain lesions.

RRMS is the most common type of MS, and around 70–80% of people with the condition have this type as an initial diagnosis.

Primary progressive MS

Primary progressive MS (PPMS) is an escalating type of MS that worsens from the time symptoms appear. There is no early remission or relapse. Symptoms may go through periods of not being active or not progressing, but they do not get better.

Individuals with PPMS may not experience exacerbations, as the symptoms get worse without remission.

Around 15–20% of people with MS have the PPMS form of the condition.

Secondary progressive MS

This form of MS, which specialists abbreviate to SPMS, is a progressive condition.

In the early stages, there are times of relapse and remission. In time, however, symptoms start to worsen without periods of remission. Exacerbation is more likely to occur in the early stages.

Every person’s experience with RRMS, PPMS, and SPMS will be different. Symptoms will vary between individuals and will progress at different rates.

Learn more about the different types of MS here.

No single test can diagnose MS or an MS exacerbation. A person may notice if pain or other symptoms increase. They may need medical help to manage worsening symptoms.

During a relapse, an MRI scan may show signs of new brain or spinal cord lesions since the previous test.

Experts believe there may be a link between high inflammation levels and these changes.

During an exacerbation, a person might find that making lifestyle changes can help improve their comfort and quality of life.

Tips include:

  • following a heart-healthy diet to reduce the risk of cardiovascular complications
  • adopting strategies to manage or reduce stress, as this may play a role in exacerbations
  • consulting the healthcare team about an exercise plan
  • considering complementary therapies, such as yoga and acupuncture
  • quitting or avoiding smoking, if applicable
  • getting someone to help with chores and complex administrative tasks

Some of these tips, such as avoiding smoking, may also help prevent exacerbations.

Individuals experiencing an exacerbation should contact a doctor as soon as possible.

Not everyone needs treatment for an exacerbation. Mild symptoms, such as fatigue, often resolve without intervention. However, a doctor may recommend treatment to manage specific symptoms, such as vision changes and muscle weakness.

For more severe symptoms, they may prescribe:

  • a high dose of steroids to help reduce inflammation
  • plasmapheresis, or plasma exchange, which involves separating plasma from the blood cells, mixing it with a protein called albumin, and returning it to the body
  • physical rehabilitation and other therapies to help with everyday living
  • counseling for mental health support

Long-term medications for MS — known as disease-modifying therapies — can help reduce the frequency and severity of exacerbations. A doctor may recommend these drugs as soon as a person receives a diagnosis of MS.

Treatment will depend on the individual, the type of MS diagnosis they have, and the symptoms involved.

The American Academy of Neurology advises that medical cannabis might also help treat some symptoms of MS-related pain and muscle problems.

What are the treatment guidelines for MS?

MS exacerbations — also known as relapses, exacerbations, or flare-ups — occur when symptoms worsen. After a while, when the exacerbation ends, the symptoms may improve or persist.

Possible triggers include infections and stress, but there may also be no noticeable trigger.

Anyone who notices a worsening of symptoms or that new symptoms appear should contact a doctor in case they need additional treatment or monitoring.