Pseudoephedrine helps some, (consult with your AME etc)
Very true, but my favourite decongestant is ACTIFED.
Everyone knows of Sudafed (pseudoephedrine) which is openly on display in chemists, and even advertised on TV. ACTIFED has an extra ingedient (pseudoephedrine plus triprolidine), and works much better in colds, catarrh, snuffles, etc etc. It's not on open display, not advertised, and needs to be specifically asked for. Packets of 12 tablets. One tab x 3-4 times daily for most adults.
Still best to ask your AME advice though, 'cos in a very few people might just produce a little temporary drowsiness. Mind you, if you've got that bad a cold . . . . . should you be flying at all ?