Nail fungus may occur anytime, whether on fingernails or toenails. The medical term for this condition is Onychomycosis. The main cause of this infection is dermatophytes, a kind of yeast that tends to spread all over the whole nail structure. Toenail fungus infection is one of the most common nail-related issues that everyone is more likely to experience at least once in a lifetime, regardless of age. Even though, toenail fungus infection is not a serious health condition, it must be addressed accordingly. It may cause pain and total loss of the nail when left untreated.