Toenail fungus, or onychomycosis, is a common infection caused by fungi, leading to thick, discolored, and brittle nails. It often starts as a white or yellow spot under the nail tip and can spread deeper, causing the nail to crumble and separate from the nail bed. Risk factors include warm, moist environments, tight shoes, and poor foot hygiene.

Treatment options include topical antifungal creams, oral medications, and laser therapy. Maintaining clean, dry feet and wearing breathable footwear can help prevent infection. Early treatment is essential to restore nail health and prevent the spread of the fungus to other nails.