The thing that kept cropping up time and time again, was something called " Post Exertional Malaise " ( PEM )
Feeling wiped out for days after long bouts of exercise, very similar symptoms to M.E.
It`s really baffling all the experts, as the conventional wisdom, is that exercise is beneficial and aides the return to health, after sickness.
You`ll find stuff online, from top end endurance runners, who are now struggling to complete easy 10k`s months and months after having had covid.
The hayfever tablets, came about by pure chance, as a couple of runners, who suffered from hayfever, found that once hay fever season had arrived and they started taking their tablets, their post covid symptoms lessened when running and then came back when they stopped taking the tablets.