Itching inside the toenail may be related to causes such as onychomycosis, onychomycosis, and tinea pedis. 1. Nail groove infection: purulent bacterial infection of the nail groove and its surrounding tissues formed along the sides of the toenail can lead to local redness, swelling, heat and pain, which may be accompanied by symptoms of itching inside the toenail. 2. Onychomycosis: the fungus invades the nail plate and/or nail bed, and the toenail may become brittle or thickened, cracked, uneven and so on, and a few patients may have the symptom of itching. 3. Tinea pedis: fungal infection of the skin of the feet, may appear small blisters, localized erosion, peeling, itching and other symptoms, usually also feel itchy toenails inside. It is recommended that the itchy toenail inside the person go to the hospital in time, clear cause, under the guidance of the doctor for standardized treatment.