I finished all my chemo etc treatment for cancer in September, and my Doctor advised me to try and wear a surgical mask whilst in the airport and plane, to try and avoid catching any "germs" as my immunity was still a bit low. I wrote an email to Ryanair to ask if they had any objections...but did not receive a reply (quelle surprize!)
In the event I wore the mask in the departure lounge but took it off through the customs search, explaining why I wore it..no problem. I put it back on in the crowded departure lounge -no problem (good side effect people gave me space!) I took it off as I walked across the tarmac, breathing in lots of fresh air and then ask the stewardess if they minded me wearing it on the plane, due to lack of immunity and they were quite happy about it. (Again no one wanted to sit by me..wonder why??)
Did the same at Stansted without hassle and on the return journey....Touch wood so far I do not seem to have the usual "Ryanair Cold" that we all seem to get from recycled air syndrome.
SO...if you have to travel, even several months after chemo, it pays to ask and not feel embarressed at wearing a mask, on planes, boats or trains.or even buses!