The most common diagnosis for white discolouration of the nail, onychomycosis is present in 2-5% of the population. When the disease is advanced, the nail becomes yellow and crumbly. Sometimes it can occur after skin infection, or due to skin infection, and occurs most often due to a fungal organism. It is very hard to treat nail infections with topical agents, therefore, consultation with a podiatrist can guide you to a proper oral treatment for your nail infection if needed.