Seasonal allergies, such as hayfever, are often exacerbated by eating foods that are challenging to your system. For many people their seasonal allergies are significantly reduced, or even eliminated completely, by avoiding wheat and cutting down on dairy products.  Other potential problem foods are oranges (and orange juice), tomatoes and soya.  It is worth keeping a food diary for a good two weeks to see if you can identify any change in how you feel. Good foods to include to support the immune system and reduce histamine reactions are berries, cherries, red onions and apples. The herb astragalus is also helpful for strengthening immunity.

It is also important to stay well hydrated as the mast cells that produce histamine are more likely to react if you are dehydrated. Drink 2 litres of water or herbal teas a day.

Herbs such as butterbur (petasites) and feverfew can also be helpful against hayfever symptoms.
But they need to be taken on an ongoing basis as they do not.