Thick, discolored toenails

Toenails that turn thick, yellow, brown or white, crumble at the edges or lift from the nail bed are common, especially as people age. The most frequent cause is a fungal infection called onychomycosis, but injuries, psoriasis and other conditions can look similar (AAD). Because the right approach depends on the cause, the first step is figuring out what is actually going on.

Why toenails change

Fungi live on the dead tissue of skin, hair and nails. Fungal nail infections often start after athlete’s foot and affect toenails more often than fingernails. Risk rises with age and with diabetes, poor circulation, nerve damage in the feet, small nail injuries, skin that stays moist for long periods, immune problems, a family history and shoes that do not let feet breathe (MedlinePlus). Nails thickened by repeated pressure from shoes or sports, or by nail psoriasis, can look almost the same. A dermatologist or podiatrist can test a nail clipping or scraping under a microscope or with a lab culture to confirm fungus (AAD).

Everyday habits that help

• Keep feet clean and dry. Dry carefully between the toes, change damp socks and choose breathable shoes (MedlinePlus).
• Treat athlete’s foot early, since it often comes before nail infection.
• Do not share nail tools, and wear sandals in gym showers and pool areas.
• Trim nails straight across and file down thick areas gently, or have a podiatrist do it if you cannot reach or see your feet well.
• Rotate shoes so they dry out between wearings.

Treatments with real evidence

Nail fungus is hard to clear. MedlinePlus says over-the-counter creams and ointments usually do not help, and that prescription antifungal pills taken for about two to three months for toenails clear the fungus in about half of people. Doctors may run blood tests to check the liver during treatment. Even when treatment works, a new healthy nail can take up to a year to grow, and the infection may return (MedlinePlus). Prescription topical solutions such as efinaconazole and tavaborole have performed better than placebo in large trials, usually with close to a year of daily use (Foley et al., 2020). Dermatologists may also prescribe maintenance treatment to help prevent the infection from coming back (AAD).

What about oils and home remedies?

Products such as Kerassentials combine ingredients like undecylenic acid and tea tree oil with other plant oils and vitamin E. Some of these have antifungal activity in the lab, and tea tree oil produced modest results in one toenail trial (Buck et al., 1994). The American Academy of Dermatology says small studies of tea tree oil and mentholated ointments suggest there may be some benefit, but their effectiveness and side effects are still unknown (AAD). Oils can make nails and cuticles look better, but they are not a substitute for diagnosis, and some essential oils cause skin allergies. If you try one, use it alongside, not instead of, a clinician’s advice.

When to see a doctor

See a dermatologist, podiatrist or primary care doctor if nail changes do not go away, if you are not sure the cause is fungus, or before starting a long course of any treatment. Get care promptly if a toe becomes painful, red, swollen or drains pus (MedlinePlus), or if the changes are spreading to other nails or the surrounding skin. People with diabetes, poor circulation, numbness in the feet or a weakened immune system should not self-treat: in a large study of people with diabetes, nail fungus was linked to a higher risk of foot ulcers, skin infections and foot surgery (Watjer et al., 2024). Daily foot checks and regular podiatry visits are worth it if you have diabetes.