An MS attack, also called a relapse or exacerbation, lasts anywhere from a few days to several weeks or even months. To qualify as a true relapse, symptoms must persist for at least 24 hours and occur without an infection or other trigger. Most attacks peak within days to a couple of weeks, then gradually improve, though the recovery timeline varies widely from person to person.
What Counts as a True Relapse
Not every flare-up of symptoms is a genuine MS attack. Neurologists use three criteria to distinguish a real relapse from a temporary worsening. The episode must last at least 24 hours, it must happen at least 30 days after the previous relapse, and it must occur without an infection or other identifiable cause. If your symptoms clear up in a matter of hours, or if they appeared alongside a urinary tract infection or a fever, what you experienced likely wasn’t a relapse at all.
What Happens During an Attack
A relapse is driven by inflammation in the central nervous system. The immune system mistakenly attacks the protective coating around nerve fibers, called myelin. When that coating is damaged, nerve signals slow down or get disrupted entirely, producing the symptoms you feel: numbness, vision problems, weakness, balance issues, or cognitive fog, depending on where the damage occurs.
The active inflammatory phase is what determines the “attack” window. Once inflammation subsides, the body begins repairing what it can. Some myelin can be rebuilt, and nerve pathways can reroute around damaged areas, which is why many people recover partially or fully after a relapse. But the repair process is slower than the damage itself, which is why recovery often takes longer than the attack.
Typical Duration and Recovery
The attack itself, meaning the period when symptoms are actively worsening or at their peak, often lasts days to a few weeks. Recovery from that attack, however, can stretch considerably longer. Some people bounce back within a few weeks. Others notice gradual improvement over two to three months or more. In some cases, certain symptoms linger indefinitely as residual effects, even after the relapse is technically over.
Early relapses in the course of MS tend to recover more completely than later ones, though this isn’t a rule. The location and severity of the inflammation matter too. A mild sensory relapse causing tingling in one hand may resolve entirely in a couple of weeks, while a relapse affecting vision or mobility could take months of recovery and still leave some lasting change.
How Treatment Shortens an Attack
High-dose corticosteroids are the standard treatment for significant relapses. They work by reducing the inflammation that’s causing nerve damage, offering rapid symptom relief and speeding up neurological recovery. A typical course involves several days of treatment, either through an IV at an infusion center or sometimes with high-dose oral medication at home.
Steroids don’t change the ultimate outcome of a relapse, meaning they won’t prevent residual symptoms that would have occurred anyway. What they do is compress the timeline. An attack that might take six to eight weeks to improve on its own may start resolving within days of treatment. For people dealing with vision loss, severe weakness, or symptoms that interfere with daily functioning, that faster recovery matters significantly.
Pseudo-Relapses: When It Feels Like an Attack but Isn’t
A pseudo-relapse mimics the symptoms of a real attack but isn’t caused by new inflammation. Instead, it happens when something temporarily interferes with nerve signals that are already weakened from previous damage. Common triggers include heat exposure, physical exhaustion, stress, and infections like a cold or urinary tract infection.
The key difference is duration. Pseudo-relapses are short-lived. Once your body temperature returns to normal or the infection clears, symptoms generally improve. This is sometimes called Uhthoff’s phenomenon when heat is the trigger. If you notice that a hot shower, exercise, or a warm day makes your existing symptoms flare and then settle, that pattern points to a pseudo-relapse rather than new disease activity.
Distinguishing between the two matters because a pseudo-relapse doesn’t require steroid treatment. It does, however, tell you something useful about your triggers, which can help you manage day-to-day life more effectively.
What Affects How Long Your Relapses Last
Several factors influence both the severity and duration of an attack. People on disease-modifying therapies tend to have fewer relapses, and the ones they do have are often milder and shorter. The specific area of the central nervous system that’s affected plays a role too. Spinal cord relapses, for example, tend to recover more slowly than those affecting sensory nerves.
Your overall health during the relapse also matters. Adequate rest, managing stress, and treating any concurrent infections can support faster recovery. Relapses that go untreated or that occur back-to-back with limited recovery time in between carry a higher risk of leaving permanent deficits, since the nervous system has less opportunity to repair between bouts of damage.
Tracking your relapses, including when they started, what symptoms appeared, how long they lasted, and what seemed to help, gives your neurologist a clearer picture of your disease activity. That information directly shapes decisions about whether your current treatment plan is working or needs adjustment.