I have an allergy to mould that gets set off if someone with a bit od mould on their clothing walks past me, and it can lead to breathing difficulties if there is enough of it. Some of the time, I can smell it and guard against it before they get close to me but I do worry that I may be misidentified as suffering from covid-19, cold or the flu.
To make it worse, once it's set off, dust and anything that might irritate me can set it off too. Evil
A good case for PM 2.5 masks