Stinging nettles have natural antihistamine properties, and help to minimize the body's reaction to pollen and other allergy irritants. Stinging nettle tea can be found in herbal stores and tea shops.

Reishi mushrooms (their Japanese name), or Lingzhi, have medicinal antihistamine properties that can treat hay fever, among other things. Reishi has been cultivated all over the world for its myriad health benefits, though it is best known in China as the "mushroom of immortality." The mushroom contains lanostan, a substance that can help regulate the level of allergen (what your body produces in response to the presence of pollen and other common irritants) in the body. Find Reishi in a variety of forms at your local health food store. 

Quercetin is a flavonoid that treats cold sores, hay fever, and poison oak or poison ivy. Quercetin occurs naturally in many foods and is often recommended for allergy sufferers because it acts as an antihistamine. You can buy it in supplement form, or boost your intake by upping your consumption of black tea, green tea, apples, onions, raspberries, red grapes and broccoli. 

Vitamin C is a natural antihistamine and can prevent inflammation of the airways during an allergy attack or reaction to Hay Fever. Taken regularly it will help the immune system function more effectively and possibly prevent allergic reactions. Good food sources of Vitamin C are guava, bell peppers, strawberries, kiwi, kale, cabbage and oranges. Since the body simply sheds whatever vitamin C it doesn't need, it's difficult to get too much.