Gray nail refers to onychomycosis, a nail disease caused by a dermatophyte infection. Hydrogen peroxide does not play a therapeutic role in nail fungus. Hydrogen peroxide is a strong oxidizing agent, with disinfecting and bactericidal effect, on bacteria, viruses, spores have a certain inactivation, but the duration is short, gray nails are generally caused by fungal infection, external use of hydrogen peroxide can play the role of disinfecting and bactericidal effect, and can’t kill the fungus effectively. The treatment of onychomycosis is mainly based on antifungal treatment, and can be treated with local antifungal drugs, which can kill the fungus to a certain extent, such as terbinafine cream, itraconazole cream, fluconazole cream, etc., and can also be taken orally when necessary to treat this kind of antifungal drugs. Patients with onychomycosis are advised to go to the hospital in time, under the guidance of the doctor to carry out active treatment, do not self-medication.