Thickened and raised toenails may be caused by ringworm of the nail, psoriasis, furuncle and other diseases. 1. Onychomycosis: commonly known as “gray nails”, is due to ringworm infection of the nail bed caused by nail lesions. Initially, only the color of the nail changes, from normal color to yellow, the condition gradually progresses, and when it involves the whole toenail, there will be thickening of the toenail, destruction and deformation. 2. Psoriasis: a skin disease caused by environmental, genetic, immune and other factors, the typical clinical manifestation is the appearance of scaly skin erythema, and when the toenails are involved, there will be keratinization and thickening under the nail. 3. Hairy erythematous furfura: a scaly, keratotic inflammatory skin disease, mainly manifested as follicular keratinized papules, skin hyperkeratosis, and toenail involvement can be accompanied by toenail thickening, hardening and bulging changes. When the toenails become thickened and raised, it is recommended to seek professional diagnosis and treatment in the hospital.