I've just been looking, as I'm taking Sudofed - works wonders - and I'm flying at the weekend (Spamcans, rather than something bigger). I haven't managed to find anything CAA related, but it appears that the FAA don't mind it. Specifically,
http://www.aviationmedicine.com/allergy.htm
says that
The over-the-counter (OTC) medications pseudoephedrine-- the active ingredient in plain Sudafed--and the prescription antihistamines Claritin and Allegra are approved for flight deck use. Other prescription decongestants containing phenylpropanolamine and guaifenesin (as in Entex) are allowed.
Seems OK over there, so it is
probably is over hear. Anyone know for sure?