Why are my toenails yellow? Causes and treatment options

Fungal toenail infections are common, affecting about 20% of Americans.¹ Once a fungus invades, it’s often hard to eliminate and frequently returns, unless you get treatment from a health care professional.

What causes a fungal toenail infection?

You can develop a toenail fungal infection (onychomycosis) when your foot comes into contact with types of fungi, such as yeast or mold.² These organisms grow in dark, moist places such as inside your shoes. However, an infection only happens if you have a cut or cracked nail. This gives bacteria a way to get into the skin.¹

Your risk of a fungal infection increases if you:³

• Have feet that sweat excessively
• Wear shoes that aren’t ventilated
• Don’t wear socks
• Have a history of athlete’s foot
• Had a previous toenail injury
• Go barefoot in gyms and pools

A toenail infection can start as athlete’s foot, another fungal condition.² Fungal infections are also more common as you get older. As your nails get weaker and crack, they let in fungi.

What symptoms develop due to a toenail fungus?

At first, you may see white or yellow spots under the tip of your toenail. There is where the organisms that cause fungal infection entered. As the infection spreads, your toenails become thick and discolored, often taking on a yellowish color. Eventually, the infection affects the shape of the nail and makes the edges of the nail crumble.^4,2

How do you treat a toenail fungal infection?

While at-home treatment may treat mild infections, it may cause more problems. It is recommended to see a physician to treat fungal infections, like a podiatrist, family medicine specialist or dermatologist. Your doctor may look at your toenail and take a sample to send to a lab. The lab will check what kind of fungus is in your nail.

After you know what type of fungal infection you have, your doctor can:

• Remove the diseased part of the nail and give you topical medication.
• Prescribe antifungal pills for larger infections
• Thin or surgically removing the nail to get better results with a topical medication.²

Sometimes it can take over a year for the infection to clear completely, depending on a person’s lifestyle and medication adherence.⁵Surgery to remove the infected nail is also an effective way to treat nail fungus. When the infected nail is taken off, the anti-fungal medicine can be put right on the infection.² It generally takes about four to twelve months for a new nail to grow.⁶

I’ve heard that laser therapy can treat nail fungus – is that true?

The FDA has approved two types of laser treatments to make toenails look better, but not to treat the fungus.⁷ However, early studies of using laser therapy to treat fungus on its own show some promise.⁸New studies show that using both anti-fungal medicine and laser therapy together may work better than using just one of these treatments for nail fungus.⁹ As a result, some physicians may offer laser treatment in combination with medication for nail discoloration caused by nail fungus.⁴ Talk to your doctor about treatment options. Many insurance plans don’t cover alternative treatments like laser therapy. Established treatment may work better.

What happens during a laser treatment for the toenail?⁹

With laser treatment for the toenail, a laser uses gentle energy, operating on a wavelength to safely go through the nail. You can expect laser treatment to take a few minutes and will be repeated until the nail appearance improves. During the procedure, you won’t feel any pain, though you may feel warmth from the laser. Laser treatment is FDA approved for improving the appearance of nails. The heat from the laser also has some antifungal properties, making it a new consideration for fungal treatment.⁹ Your doctor will discuss treatment time and number of visits needed to improve your nail health.

Eric J. Abrams, DPM, FACFAS is a board-certified podiatrist at Optum Medical Care serving the New York and New Jersey regions. Dr. Abrams treats conditions from simple calluses to complex fractures and deformities, to Achilles tendonitis, plantar fasciitis, hammertoes, and bunions. He is currently treating patients at Optum podiatry locations in Eatontown and Toms River, NJ.

Sources:

1. Foot Care MD: Toenail fungus (onychomycosis). Accessed August 5, 2025
2. APMA. Conditions Affecting the Foot and Ankle. Accessed August 5, 2025
3. National Library of Medicine. Fungal nail infection. Last updated October 13, 2024. Accessed August 5, 2025
4. AAD. Nail Fungus: Signs and Symtoms. Last updated June 26, 2025. Accessed August 5, 2025
5. National Library of Medicine. Onychomycosis. Last Updated January 9, 2024. Accessed August 5, 2025
6. CMS. Surgical Treatment of Nails. Accessed August 5, 2025
7. AAFP. Onychomycosis: Rapid Evidence Review. Accessed August 5, 2025
8. AAD. Nail fungus: Diagnosis and treatment. Last updated June 26, 2025. Accessed August 5, 2025
9. National Library of Medicine. Carbon Dioxide Laser Plus Topical 5% Luliconazole: A Better Combination Therapeutic Modality for Onychomycosis. Accessed August 5, 2025.