Study Design: 26 week duration of follow-up, 3-arm RCT (N=75). All groups will utilize routine care for their GWI and symptoms of CRS and fatigue. Groups 1 and 2 will in addition add S-NI or X-NI twice daily to their routine care, respectively. Group 3 will continue to use routine care with no other additions (control group); control group participants will be offered NI training and related materials (xylitol or saline per subject preference) after they complete their 26-week follow-up period.