Nail fungal infections are highly common infections and caused by many different types of fungi (yeasts or molds) that live in the environment. Nail cracks, splits on the nail or surrounding the skin can allow germs to enter and cause infection. Protect and help fight against the fungus with Barielle's Fungus RX, a prescription maximum strength Nail Fungus Treatment. Barielle's Fungus RX ingredients fight against bacteria, fungi and viruses and is a high-impact, scent-free solution which is also gentle enough for those with sensitive skin.