Foreign body sensation in the eyes is usually caused by the following reasons: First, it is caused by a foreign body in the cornea, such as sand and dust entering the eye will stimulate the sensory nerve fibers of the cornea, thus causing a strong foreign body sensation in the eye. Second, due to keratitis, such as viral, bacterial or fungal infections that cause inflammation of the cornea, the sensory nerve fibers of the cornea will be in an over-sensitive state, thus causing foreign body sensation in the eye. Thirdly, due to the dryness of the cornea, the tear secretion on the surface of the eye is reduced, so that the surface of the cornea cannot be covered with a complete tear film, which does not play a protective and lubricating role and can cause foreign body sensation in the eyes. Fourthly, due to conjunctival stones, the metabolic products of conjunctival cells accumulate under the conjunctival epithelium, forming yellowish-white particles that protrude from the conjunctival surface and rub against the corneal epithelium, thus forming a foreign body sensation.