Toenails appear hard and thick, need to clarify whether it is caused by fungal infection or thick nail disease, according to the cause of treatment. 1. Fungal infection: cause thick toenails, also known as gray nails, do fungoscopy test can be a clear diagnosis, can be in the lesion nail local topical antifungal medicine, if the symptoms do not get better, need to be added to the oral antifungal drugs, need to test the liver function during the use of drugs. 2. Thick nail disease: is due to the lack of trace elements in the body, need to test trace elements, according to the test results of appropriate supplementation of trace elements, can also be applied to the nail lesions salicylic acid solution, by thickening of the toenail will gradually improve. Toenails appear hard and thick also seen in other reasons, should be timely consultation, clear cause, standardized treatment under the guidance of a professional doctor, to avoid delay in treatment.