I understand that these are supposed have a double whammy of not only protecting you from other people's germs but also to stop you spreading your own bugs around.
Actually you're on a bit of a hiding to nothing if you try to keep yourself from getting a cold and you travel on public transport, you're likely to get a "Commuting Cough". Even though yesterday's Evening Standard gave advice on avoiding the "Cough-ice". Doctor Christian of the telly, so nicely said "Being squashed together in a packed Tube carriage with the disease-ridden public will guarantee you won't escape uninfected this winter."
However he continued with something I'd agree with "Dramatic gestures such as wearing a face mask are unlikely to help much as most people pick up infections from contaminated surfaces rather than from droplets in the air...
"Struggling into work when you are ill is not valiant and dedicated, it is foolish and will only prolong your own illness and virtually guarantee that colleagues will catch your virus too. Stay home and recuperate."
You'll also see more ads like this one around for nasal sprays and the like
At least this one is Tube related with stops such as "Sniffingham", "Sick-of-being Hill"
My advice is layers, as you'll need to wrap up warm for the outside but remember the Tube is often over heated in the winter. Finally, if you do want a stylish scarf to wrap round your face when the person opposite you has a coughing fit, you might like London Transport Museum's new Routemaster Moquette Design Lambswool Scarves.
Possibly too late to order online for a Xmas pressie (they have them in their Covent Garden shop too), but it's nice for yourself at £24.95.