Composite image of nasal epithelium and pollen. Coloured Scanning Electron Micrograph (SEM) of the surface of nasal epithelium with inhaled in pollen. These allergens cause rhinitis, the inflammation of the lining of the upper nasal tract. This causes watering eyes, a runny nose and sneezing in hay fever. The surface of the nasal epithelium is made up of cells with hair-like cilia. These microscopic hair-like structures are covered with a sticky mucus (not seen) that traps inhaled particles. Coordinated, wave-like beating of the cilia propels the mucus to the back of the nose (pharynx), where it is swallowed. Magnification: x4000 when printed at 10 centimetres wide.