Sneezing into the sun is clinically common in children up to the age of three, but it is also common in adults but not very common. The reason for this is that the perception of the eyes and nose are both innervated by the same trigeminal nerve, and when the patient is facing the sun, the sunlight stimulates the patient’s eyes, so that because the nerves in these two places are mixed together, the strong stimulation is confused and causes sneezing. Specifically the strong sunlight entering from the eyes, which the nasal cavity mistakes for stimulation of itself, causes excitation of the nasal trigeminal nerve. This excitation is transmitted to the brain center causing a violent contraction of the respiratory muscles in the lungs, resulting in the manifestation of sneezing. Clinically, sneezing excretes nasal secretions, nasal fungi, bacteria, allergens, etc.