Cell danger response/immune, endocrine and nervous system dysregulation illness are on the increase. Genetic vulnerability (up to 50%) can play a role, where risk of developing a cell danger response increases with age due to inflammaging . Other causes and maintainers include toxicity, inflammation, sensitisaiton and stress. People with these concerns (including myself) can experience stress/stressor sensitivity.
For some of us (including myself) this includes sensitivity to foods like those high in histamine and food chemicals, and some other. Which may persist even with other treatments that considers a person conditions and TISS (as tolerated), if genetic vulnerability is more severe.
https://www.healthline.com/health/5-minute-guide-to-inflamm-aging