Hi Chrissy,
If you take other meds talk to your doc/chemist/health care person before taking things like flu tablets and stuff as they all may interact. I have also been told by the doc that eating a serve of oily fish weekly is good for allergies as it boosts something or other. 

The sudden onset may have to do with changes in weather, maybe it is dryer, or someone nearby has planted something that has sparked it up. Keep well, don't work too hard. Jenny