Thick nail cap may be caused by chronic onychomycosis, hand eczema, onychomycosis and other diseases. 1. Chronic onychomycosis: the occurrence of this disease may be related to long-term hot and humid environment leading to bacterial or fungal infections, or long-term repeated contact with irritants, mutagens, the typical symptom is a red rash in the nail grooves elevated, under the nails can be yellowish-green signs of infection, the nail morphology changes, such as elevation, discoloration, nail plate hypertrophy and so on, which can be manifested as a thick fingernail cap. 2. Hand eczema: the basic causes of this disease include decreased estrogen levels, heredity, bacterial infections, micronutrient deficiencies, etc. It can be triggered by frequent contact with humid environments, chemical substances, etc., resulting in itchy skin on the hands, peeling, and thick fingernails. 3. Onychomycosis: this disease is mainly caused by the pathogenic bacteria such as red trichophyton and trichophyton mustelii in dermatophytes, and the common susceptibility factors are nail trauma, local lymphatic circulation disorder, impaired immune status, and so on. The nail plate of the patient will appear cloudy, thickening, discoloration and so on, so the patient exists in the case of thick nail cover. When the patient finds that the nail cover is thick, he needs to go to the hospital to improve a series of relevant examinations to clarify the specific causes.