Oh course you can ask! lol! I just use Morrisons own brand of Heyfever tablets. I feel that they do the trick for me! I can't say I have ever noticed particualrly feelings low or headaches related to Heyfever though.
I must say though, I think I suffer with Seasonal Affective Disorder because in the months from September to sort of November I always feel particularly low. I wouldn't know if that could be linked with PKU or if it's just me as a person?!