Gray nails are caused by fungi, and the typical symptoms can be divided into five main types, with different types of nail fungal disease having their typical and other manifestations. One type is the white superficial type, where the fungus invades directly from the surface of the nail plate, and the nail plate shows white opaque, clear marginal scars or cross grooves, which can turn yellowish white over time. A kind of distal lateral sub nail type, the fungus first infects the distal nail and lateral edge skin cuticle, and then extend to the nail bed, then the nail bed can become dirty, color and hardness change, brittle increase is very easy to break insect-like. The subproximal nail type may show roughness, thickening, unevenness, or even breakage of the nail half-moon and nail root. The intralaminar type, in which the damage is mostly confined to the nail plate or invades the inferior nail, has a white or grayish-white nail plate with no obvious thickening or atrophy. Full nail plate gyrus type, this type is based on the above-mentioned types and continues to aggravate the involvement of the whole nail, showing symptoms of erosion, destruction, detachment and nail abnormalities of the whole nail plate.