Toenails separate from the nail bed for many reasons, including injuries, infections and serious illness. The most common reason involves injury as the result of repeated stubbing or jamming of the toes.
Fungal nail infection also leads to detached toenails. Symptoms of fungal nail infection include cracked, discolored or thickened nails. Chronic skin conditions such as psoriasis may result in onychomycosis, a fungal infection that causes nails to thicken.
Cancer patients may experience nail detachment because of chemotherapy, which causes discoloration and breakage of the nails. People with detached toenails need to trim and cover the area with medical tape until the new nail fully establishes itself.