What Can Trigger an MS Flare-Up? Everyone is different, but certain factors commonly trigger flare-ups in MS patients. Watch the video above to learn about these common triggers, or read the\u00a0written summary below. Stress Dealing with stress can cause symptoms to worsen. Stress can also cause depression and fatigue, which don\u2019t help symptoms, either. Fatigue Physical fatigue can impact your mobility, making walking more difficult, while cognitive fatigue can make you sluggish and forgetful. Infection and Illness Infections and illnesses, like the flu or a cold, can cause a flare-up. Do your best to avoid germs. Heat An increase in body temperature can trigger MS symptoms, making the summer months a difficult time. Stay in air-conditioned buildings, seek shade, and take cooler showers. Foods Some people find certain foods cause their symptoms to relapse. You can experiment with cutting gluten and dairy out of your diet to see if it helps. Knowing what causes your flare-ups is crucial for developing strategies to avoid them.