Anti-histamines never helped me much but just made me sleepy.
As for food allergies I try to avoid eating them, in my case raw fruit and veg, honey, avocado and legumes, certain nuts.
Of course you can't avoid stuff in the air and my hayfever this year is terrible. I've even started squirting Seretide up my nose in desperation.
What worked WONDERFULLY for me in the past was autohaematherapy with ozone and allergy ampule. You can get that in Germany (you have to pay though, the universal medical insurance doesn't cover it). In that treatment you go on a Vitamin C drip then they take some blood from your arm, mix it with ozone and the ampule then inject it back into your bum.