Gray nails, also known as onychomycosis, are usually a nail lesion on the hands or feet caused by a dermatophyte infection. The nails belong to the category of skin appendages and need to be seen by a dermatologist at a regular hospital for a clear diagnosis and targeted treatment of gray nails. Gray nails usually appear as cloudy, thickened, separated, discolored, atrophied, peeling, buckling, uneven surface, etc. They may also appear as painful and bleeding under the nail. Patients should visit a hospital promptly. During the dermatology interview, a nail fungal smear microscopy and culture are required. After a clear diagnosis is made, the doctor will usually choose an appropriate treatment plan according to the condition and different causative organisms. Currently, oral terbinafine and itraconazole are recommended for antifungal treatment in clinical practice, and topical treatment with terbinafine ointment and sertaconazole nitrate ointment can also be chosen. In case of distal nail plate involvement, macular striated nail, ingrown nail or nail plate thickness >2mm, nail extraction or removal of diseased nail is required. In addition, gray nails can be treated with laser therapy and photodynamic therapy to inhibit fungal growth.