Neglecting toenail fungus, formally known as onychomycosis, can lead to severe health consequences, warns Dr. Peter Joseph, a podiatrist at Allegheny Health Network.Beyond being an aesthetic concern, untreated toenail fungus can cause foot discomfort, making walking challenging due to the thickening and misshaping of infected nails, especially while wearing shoes.The warm, moist environment inside shoes provides an ideal breeding ground for the fungus, leading to athlete’s foot—a condition characterized by red, itchy, and cracked skin.watch below..