Plants release microscopic pollen granules into the air at certain times of the year as part of their reproductive process. Regardless of whether pollen comes from trees, grass or grasses, it can cause sneezing in some of us as a final consequence of the release of histamine in the nose.
For those with allergic sensitivity, the process begins when specific proteins in the airborne pollen enter the nose when we breathe it. These proteins are linked with antibodies (known as immunoglobulin E) in the bloodstream. When the antibodies are connected to mast cells and basophils in the nasal mucosa, the compound known as histiamine and other inflammatory mediators is released.
Histamine irritates nerve cells in the nose, resulting in signals to the brain that trigger sneezing through the trigeminal nerve network. This nervous network controls the sensations and movements of the face. The end result is the coupling between the brain and the muscles of the pharynx and trachea to create a large opening in the oral and nasal cavities, followed by a powerful release of air and bioparticles.
This whole process serves to purge the body of the allergenic particles and proteins it has ingested. Because histamine triggers this immune system response, oral and nasal antihistamine medications are effective in blocking the compound in the areas where it is present. Nasal corticosteroids can also control sneezing and other symptoms of nasal allergy by reducing the inflammation present in the nose at any time.