Onychomycosis, also known as toenail fungus, is a common fungal infection that affects the nails on the toes and sometimes fingers. It is characterized by thickened, discoloured, and brittle nails that may become painful and emit a foul odour. It is important to note that not all nail deformities or discolouration are caused by fungal infections. Onychomycosis can be caused by various factors, including poor hygiene, wearing tight-fitting shoes, nail trauma, and a weakened immune system. Diabetes and other underlying conditions make you more susceptible to fungal nail infections.

Treatment options include topical or oral antifungal medications, laser therapy, regular nail debridement, and, in severe cases, surgical removal of the affected nail. It's important to see a podiatrist if you suspect you have onychomycosis, as it needs specific diagnosis and testing, can be difficult to treat, and may lead to complications if left untreated.