Lupus flare-ups happen when the disease is at its most active. These flare-ups, or relapses, are unpredictable. Some people may experience flare-ups every few years. Others may have them with greater frequency. Lupus flare-ups can occur at any time, and last anywhere from several days to a few weeks or more. They can vary in severity, ranging from mild to life-threatening. Bouts of remission, when people with lupus don’t have any symptoms, are common following a flare-up. Unfortunately, we don’t know why this cycle of flare-up and remission occurs or why it is so unpredictable.