The appearance of double-layered nails can be manifested as obvious thickening of the nails, etc. This condition may be related to diseases such as onychomycosis, onychomycosis, psoriasis nail injury, etc., and may also be related to trauma. Onychomycosis is a skin disease caused by fungal infection of the nail, in which the main clinical manifestations are thickening of the nail plate, discoloration of the nail plate as well as local warping of the shells, empty shells, etc., and the symptoms of double-layered nails may appear. Nail lichen planus is a chronic inflammatory skin disease that occurs in the nail area, the etiology of which has not yet been clarified, and may be related to genetic, immune, infection and other factors. Clinically, it mainly manifests as thickening of the nail plate, roughness of the nail plate and unevenness of the nail plate surface, and the symptoms of double-layered nails may appear. Psoriasis nail injury is psoriasis patients appear nail involvement, in the clinical mainly manifested as nail surface pitting depression, nail plate thickening, nail plate rupture peeling and loss of luster, etc., may also appear double nail symptoms. In addition, trauma can also affect the nail plate and nail bed, which can lead to morphological changes in the newborn nail plate, which is also the main cause of double-layered nails. As there are many causes of double-layered nails, it is recommended that patients go to the dermatology department of regular hospitals for a clear diagnosis and standardized treatment under the guidance of doctors.