Thank you for your very topical question! Hayfever (in medical terms known as seasonal allergic rhinitis) is caused by a hyperactive immune response to inhaled particles known as allergens. Allergens can include dust and pollution but are most often consisting of pollen particles which is why they are associated with this specific time of year. To improve symptoms one must aim to balance your immune response. Natural remedies include tumeric (curcumin), quercetin, omega 3&6, vitamin C and zinc.
Foods to eat include your dark green leafy vegetables, root vegetables such as carrots, beetroot and horseradish, as well as ginger, onion and garlic. Try to reduce your consumption of dairy, citrus, red meat and wheat. A homeopath friend of mine also recommends eating organic honey farmed in your area to further improve your symptoms.