The sneeze reflex is triggered by the stimulation of specific receptors of the trigeminal nerve, present in the nasal cavities, in the oral cavity and in the pharynx. These receptors can be stimulated directly by contact with irritating substances, but also indirectly by chemical mediators released by some white blood cells.
A good part of the trigeminal nerve receptors is in fact sensitive to histamine, a substance released by some cells of the immune system (basophils and mast cells) following an allergic stimulus.
The activation of these histamine-sensitive receptors also includes rhinorrhea (runny nose) and itching sensations, often associated with sneezing in allergic pictures.
Antihistamine drugs are useful in inhibiting sneezing especially because they bind to histamine receptors, inhibiting their activity.
