Foot big toe nail empty, may be caused by onychomycosis, nail dystrophy, psoriasis, etc., to determine the symptoms of the cause, need to be based on the patient’s main performance, signs, auxiliary examination analysis. Several common conditions are: 1, ringworm: dermatophytes invade the nail plate, nail beds leading to nail lesions, nail plate showing turbidity, thickening or brittle, discoloration, shedding, etc., commonly known as gray nails. After the toenail is infected with fungus, the moistness or glossiness of the toenail will be reduced, and the seriousness will cause the integrity to be damaged, which is usually manifested as the hollow under the toenail. Tinea cruris is mostly caused by direct infection of tinea cruris, and fungal microscopy and culture is the gold standard for the diagnosis of tinea cruris; 2, nail dystrophy: toenail dystrophy, the normal formation process is affected, which manifests itself as changes in the shape, texture, structure and color of the nail, and it may result in hollow toenail, accompanied with thinning and thickening of the nail, and the emergence of white spots on the toenail and vertical lines on the toenail, etc.; 3, nail psoriasis: that is, psoriasis occurring on the toenail, which is mainly Local damage caused by psoriasis, manifested as uneven nail plate, thimble-like punctate depression on the nail plate, resulting in brittle toenails, loss of luster, possible longitudinal ridge, transverse grooves, turbidity, hypertrophy, and easy peeling of the nail bed and the free end, the etiology of which is currently unknown. In addition, nail defects may occur in a variety of hereditary skin disorders, often accompanied by developmental abnormalities in other organs, including the skin, teeth, brain, and bones. In addition to congenital factors, nail defects may also be caused by skin diseases, local injuries, nail tumors, etc. It is recommended to actively go to the hospital for relevant diagnosis and treatment.