Nail fungus is a common condition that begins as a white or yellow spot under the tip of your fingernail or toenail. As the fungal infection goes deeper, nail fungus may cause your nail to discolor, thicken and crumble at the edge. It can affect several nails but usually not all of them.
If your condition is mild and not bothering you, you may not need treatment. If your nail fungus is painful and has caused thickened nails, self-care steps and medications may help. But even if treatment is successful, nail fungus often comes back.
Nail fungus is also called onychomycosis (on-ih-koh-my-KOH-sis) and tinea unguium. When fungus infects the areas between your toes and the skin of your feet, it’s called athlete’s foot (tinea pedis).
Nail fungal infections are typically caused by a dermatophyte fungus. 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. Others cause illness and infection. Fungi:
- Live in warm, moist environments, including swimming pools and showers
- Can invade your skin through cuts so tiny you can’t even see them or through a small separation between your nail and nail bed
- Can cause problems if your nails are often exposed to warm and moist conditions
Toenails vs. fingernails
Nail fungus occurs more often in toenails than in fingernails, partly because:
- Toenails often are confined in a dark, warm, moist environment — inside your shoes — where fungi can thrive
- Toes usually have less blood flow than do fingers, making it harder for your body’s immune system to detect and stop infection
You may have nail fungus — also called onychomycosis (on-ih-koh-my-KOH-sis) — if one or more of your nails are:
- Brittle, crumbly or ragged
- Distorted in shape
- Dull, with no 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 (on-ih-KOL-ih-sis). You may feel pain in your toes or fingertips and detect a slightly foul odor.
When to see a doctor
You may want to see a physician if self-care steps haven’t helped. Also see a doctor if you have diabetes and think you’re developing nail fungus.