Medically Reviewed by Gabriela Pichardo, MD on May 27, 2020
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What Happens During a Relapse?

When you experience a multiple sclerosis relapse (also known as an exacerbation or flare-up), it's because new damage in the brain or spinal cord disrupts nerve signals. That's why you might notice new symptoms or the return of old symptoms. A true relapse lasts more than 24 hours and happens at least 30 days after any previous relapses. Relapses vary in length, severity, and symptoms. Over time, symptoms should improve. Many people recover from their relapses without treatment.

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Damage to the protective covering of nerve fibers interrupts normal signals from the brain to the body. When those signals are disrupted, your body doesn't function like it once did. Things you did easily before can seem difficult -- like opening a jar or turning a doorknob. Sudden or worsening weakness that doesn't go away could mean you're having a relapse.

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Vision Problems

If your vision is blurred or you're seeing double, you could be starting to relapse. Some people also lose their depth or color perception as the optic nerve becomes inflamed. Taking a hot shower or bath or having a viral infection like the flu can sometimes trigger vision problems, but these are only temporary and should go away within a day.

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Numbness or Tingling

Numbness is one of the most common signs of a multiple sclerosis relapse. You can lose so much feeling that it's hard to use your hands or other affected body parts. You might not be able to write or hold a coffee cup. If numbness is new or getting worse, it's time to call your doctor.

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Thought Problems

It's frustrating to forget where you left your car keys, or to have to re-read the same paragraph over and over just to understand it. MS can affect your mind in many ways, interfering with memory, concentration, language, and information processing, especially as the disease progresses. Any new trouble thinking clearly or remembering past events is a warning that you could be in the midst of a relapse.

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Feeling lightheaded or unsteady on your feet can be an unsettling experience, but it's a common sign of MS relapses. The dizziness is due to damage in the parts of your brain that control equilibrium. A motion sickness drug can take away that 'room-is-spinning' feeling in the short term, but if it lasts more than a day you may need to be treated for an exacerbation.

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Balance and Coordination

"Somebody may start to feel like they're drunk when they walk, or they [may] have trouble coordinating movements in their arm," says John Ratchford, MD, MSc, assistant professor of neurology at the Johns Hopkins University School of Medicine. Muscle weakness or spasm, numbness, and a loss of balance during a relapse can make you uncoordinated and unsteady on your feet.

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Does Heat Trigger Relapses?

Soak in a hot tub or sit outside on a muggy day and you might feel like you're having a flare-up -- but you're not. "There's a lot of confusion among patients about heat," says Aaron Miller, MD, medical director of the Corinne Goldsmith Dickinson Center for Multiple Sclerosis at the Mount Sinai School of Medicine. Heat may bring on MS symptoms, but they'll go away as soon as you cool off.

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What Causes a Relapse?

A recent bout of the flu or other infection can trigger an MS relapse, some studies have suggested. Other suspected triggers are less certain, including stress, which is hard to study because it affects everyone differently. "I think it's quite possible that for some people, stress can have effects on the immune system and potentially increase the risk for a relapse," Ratchford says.

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Preventing Relapses

The best way to prevent relapses is to take the medicine your doctor prescribes. "All of the medicines we use for relapsing MS have been shown to reduce the frequency of relapses -- that's the main reason they were approved," Miller says. Eating well, sleeping enough, and reducing stress are also good advice. Call your doctor if any new symptom appears or gets worse, and doesn't go away after 24 hours.

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Treating Relapses

Not every relapse needs to be treated. If movement isn't limited and you're not uncomfortable, your doctor might recommend waiting until the symptoms improve on their own. For more bothersome exacerbations, intravenous steroids can speed recovery. Sometimes plasma exchange -- removing the blood and replacing the liquid part -- is used to treat more severe relapses.