Gray nails are infections of the nail plate or nail tissue caused by fungal infections, also known as onychomycosis, and are somewhat contagious. There are many fungi that trigger gray nails, and the following are common: 1. dermatophytes: gray nails are mainly caused by dermatophyte infections, of which Trichophyton rubrum infections are the most common, followed by Trichophyton spp. and Flocculus epidermidis. 2. non-dermatophytes: for example, yeasts and certain molds, the main ones being Candida, Malassezia, and Short Broom Mycobacteria. May also be spores, Fusarium and other rare fungal infections. These fungi are present in daily life, and contact with public baths or pools with poor hygiene, as well as keeping pets such as cats and dogs, may infect the pathogenic fungi and lead to gray nails. Clinically, there is no significant difference in the symptoms of gray nails caused by different fungal infections, and there is no significant difference in the medication used. Currently, oral terbinafine and itraconazole are recommended in clinical practice for antifungal treatment, and glacial acetic acid solution can also be chosen for topical treatment, all of which should be used under the guidance of dermatologic medical staff. Nail extraction or removal of diseased nails is required when necessary, and laser and photodynamic therapy can also be used as an adjunct and alternative treatment for gray nails.