Nail fungus is a fungal infection in one or more of your nails. An infection with nail fungus may begin as a white or yellow spot under the tip of your fingernail or toenail. As the nail fungus spreads deeper into your nail, it may cause your nail to discolor, thicken and develop crumbling edges – an unsightly and potentially painful problem.

Causes

Nail fungal infections are typically caused by a fungus that belongs to a group of fungi called dermatophytes. But yeasts and molds also can be responsible for nail fungal infections.

What are fungi?

Fungi are microscopic organisms that don’t need sunlight to survive. Some fungi have beneficial uses, while others cause illness and infection.

All of these microscopic organisms:

• Live in warm, moist environments, including swimming pools and showers
• Can invade your skin through tiny visible or invisible cuts or through a small separation between your nail and nail bed
• Cause problems only if your nails are continually exposed to warmth and moisture – conditions perfect for the growth and spread of fung

Symptoms

There are different classifications of nail fungus – depending on type of fungus and manifestation – which may have somewhat different signs and symptoms. In general, however, you may have a nail fungal infection if one or more of your nails are:

• Thickened
• Brittle, crumbly or ragged
• Distorted in shape
• Dull, with no luster or shine
• A dark color, caused by debris building up under your nail

Infected nails also may separate from the nail bed, a condition called onycholysis. You may feel pain in your toes or fingertips and detect a slightly foul odor.