Cracked toenails may be caused by exogenous irritation, onychomycosis and other factors. 1. exogenous stimulation: patients with trauma to the toenail or long-term contact with water, chemical irritants, the nail plate is easy to become rough, brittle texture, there may be cracks in the toenail. 2. Onychomycosis: usually the toenail is locally infected by fungus, which can destroy the structure of the toenail deck through keratinase, thus leading to cracks in the toenail. It is recommended that patients protect their nails, and if they have cracked toenails, they should go to the hospital in time for treatment under the advice of a doctor.