An allergy occurs when your body develops an immune response to allergens which creates antibodies. The antibodies then activate receptors on your cells which results in a release of histamine, causing an allergic reaction (puffy eyes, runny nose, etc). Similarly to over-the-counter allergy medications, bee pollen reduces histamine release which helps to lessen or eliminate allergic reactions
If you are a beginner, introduce bee pollen into your diet slowly, a granule or two at a time. The optimal serving of pollen varies with individual needs. You should gradually increase your serving to one tablespoon a day.