Over 9,000 species of grass are currently in existence and only a small percentage of those are known to cause allergic reactions in humans. Included in the allergy-causing grasses is timothy, which contains a protein called PHL P II in its pollen grains. PHL P II is one of the world’s major plant allergens and, until recently, the only method for its control has been antihistamine medications. Scientists are, however, currently attempting to create a synthetic hypoallergenic vaccine that would provide easy, ongoing relief for many of those that suffer from pollen allergies.