Nail fungus, also called onychomycosis, is a common condition in which a fungal organism infects the fingernails or toenails. Fungal infections of the nails are normally minor ailments, easily treated with antifungal medication. Nail fungus is often caused by the same organisms that cause jock itch, athlete’s foot, and ringworm. 

Symptoms of nail fungus include thickening of the nails, discoloration of the nails (typically a whitish to yellow or brown coloring), distortion of nail shape, brittle or crumbling nails, and an unpleasant odor. While it may affect fingernails, nail fungus is far more common in toenails. 

Risk factors for nail fungus include being older, sweating heavily, a history of athlete’s foot, and walking barefoot in areas where infection may be more likely (such as public pools, gyms, shower rooms and other damp communal areas). Minor skin conditions, such as psoriasis, may also increase the likelihood of nail fungus, as may certain more serious medical conditions, for example, diabetes, a weak immune system, or circulation problems. 

Preventative measures are often effective in minimizing the likelihood of nail fungus outbreaks, such as maintaining good foot hygiene, washing hands after touching an infected nail, wearing sweat absorbing socks and breathable shoes, and using footwear in public areas.

Nail fungus may be treated with over-the-counter antifungal medication, but should this prove ineffective there are prescription drugs available. Drug classes commonly used to treat nail fungus are azole antifungals, topical dermatological antifungals, systemic dermatological antifungals, other systemic antifungals, and other dermatological preparations.