Similarly, some people with ME/CFS may fear pain from triggering or exacerbating existing metabolic symptoms such as mast cell activation syndrome (MCAS), post-exertional malaise (PEM), inflammation, sleep deprivation, etc, leading them to increasingly avoid foods, supplements and people, along with physical and mental activities. This avoidance can result in severe deconditioning, increased isolation, and a greater severity of symptoms, perpetuating a closed-loop / cycle of fear and avoidance.