Has anyone used doxycycline or another old-school antibiotic?

Has anyone had success using doxycycline or other old-school antibiotics for treating…or at least managing…systemic inflammation? Once upon a time (before COVID) a dermatologist prescribed doxycycline when I had recalcitrant inflammation/rosecea on my face and legs. It worked very well. Would it possibly treat the inflammation in my body that I can’t see? And also possibly quell any other lingering bacterial infections? Grasping at straws (3 years in, age 81), but don’t want to do anything (too!) foolish.