Terbinafine can be used to treat gray nails, which are also known as nail fungus and are caused by fungal infections that damage the nails. Terbinafine is an effective oral medication for treating fungal infections, so terbinafine can be used to treat gray nails, and topical medications are generally difficult to penetrate. For nail fungal disease more extensive than half a nail, are given oral antifungal drug treatment, such as terbinafine, itraconazole, fluconazole can be taken orally. The nails of the hands require more than 3 months of continuous medication, while the toenails require more than 4 months of continuous medication. Since most antifungal drugs are metabolized by the liver, you need to check your liver function regularly while taking the drugs and avoid drinking alcohol. For those with abnormal liver function, you need to adjust the medication according to the liver function.