A fungal infection of the nail (onychomycosis) is usually caused by dermatophytes (true fungi) and rarely by yeast or candida. The fungal infection often penetrates an injured nail through the cuticle and may discolor the nail, leading to increased debris at the edges of the nail, lifting of the nail, and the nail can fall off. Once you had a fungal infection in a nail, the likelihood of recurrence of fungal infection significantly increases. Diagnosis involves a nail clipping for culture and histology. So, allowing the affected nail(s) to grow long for this clipping is very important. The treatment can be an oral medication or a paint-on medication.