If the toenail is thick and hard, you need to distinguish whether it is congenital thick and hard toenail, or acquired thickening and hardening, the common causes are as follows: a. Congenital factors: congenital thick nail disease is a rare nail hypertrophy genetic skin disease, patients can appear in infancy toe nail significant hypertrophy, accompanied by sweating, dry skin, scaling, cracking and other symptoms. Local application of keratolytic agents, such as lactic acid lotion, salicylic acid and urea preparations, oral treatment with retinoic acid, and also nail extraction, nail matrix and nail bed scraping treatment can be carried out. Second, acquired factors: 1, friction stimulation: due to long time wearing too narrow shoes or too tight socks, may make the toenail long-term friction stimulation, resulting in toenail gradually thickened and hardened. In this case, attention should be paid to the comfort of socks and shoes, and no special treatment is usually required. 2. Fungal infection: If the toenail is infected by a fungus, it can lead to onychomycosis, commonly known as gray nails. The fungal infection causes a constant build-up of keratin in the nail plate, making the nail plate thicker, and the diseased nail is usually more than 2-3 times thicker than a healthy toenail. Patients need to go to the hospital promptly to get a clear diagnosis through a fungal smear. After diagnosis, oral antifungal treatment with terbinafine and itraconazole is prescribed, and topical treatment with terbinafine ointment and sertaconazole ointment is also available.