Toenail Discoloration Causes 2026: When to Worry | DPM

Quick answer:Toenail discoloration — yellow, brown, white, green, or black — is most often from fungal infection, injury, or staining by polish, and only rarely from something serious like melanoma. Our Michigan podiatrists identify the cause and treat it, and evaluate any dark streak promptly. Call (810) 206-1402.

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Township, MI. Last updated April 2026.

Toenail discoloration — nails that change to yellow, black, white, green, or brown — is one of the most common concerns bringing patients to Balance Foot & Ankle in Southeast Michigan. While some nail color changes are cosmetic nuisances, others signal systemic disease, infection, or rarely, malignancy. Dr. Tom Biernacki provides a clear, practical explanation of what different nail colors typically mean and when evaluation is warranted.

Yellow Toenails

Yellow nails are most commonly caused by onychomycosis (toenail fungal infection), the most prevalent nail disorder in adults. Fungal nails are yellow to brownish, thick, crumbly, and often have a subungual (under-nail) debris accumulation. They may lift away from the nail bed (onycholysis). Diagnosis is confirmed by nail clipping culture or PCR test — treatment depends on the extent of involvement and patient health factors. Other causes of yellow nails include: nail polish staining (the most benign cause — resolves with a break from polish use); psoriasis (which also causes pitting and oil spots on the nail); yellow nail syndrome (a rare condition associated with lymphedema and pulmonary disease); thyroid disorders; and prolonged use of tetracycline antibiotics.

Black Toenails

Black (or dark red-brown) toenails are most commonly caused by subungual hematoma — blood under the nail from trauma or repetitive microtrauma in runners (runner’s toe). Traumatic hematoma is usually identifiable by clear preceding injury or activity history and fills a large portion of the nail uniformly, growing out with the nail over months. The critical “can’t miss” cause of a dark nail without clear traumatic cause is subungual melanoma — a malignant melanoma under the nail that appears as an irregular, streaky dark band (melanonychia striata) that does not grow out, may extend onto the nail fold (Hutchinson’s sign), and requires biopsy. Any dark nail pigmentation without a plausible traumatic cause should be evaluated by a podiatrist or dermatologist.

White Toenails

White nail discoloration has several patterns with different causes. Superficial white onychomycosis (white patches on the nail surface that can be scraped off) is a fungal infection of the surface nail keratin — treated topically. White lines across the nail (Mees’ lines or Beau’s lines) reflect systemic stressors — major illness, chemotherapy, arsenic poisoning, or severe nutritional deficiency — that interrupted nail growth temporarily; these lines grow out over months. Complete white nails (leukonychia totalis) may be genetic or associated with liver disease (Terry’s nails, where the proximal nail is white with a narrow pink band at the tip) or other systemic conditions. Apparent leukonychia (where the nail appears white due to changes in the nail bed, not the nail plate itself) may indicate renal disease, cirrhosis, or hypoalbuminemia.

Green and Other Color Toenails

Green nails (chloronychia) are characteristically caused by Pseudomonas aeruginosa bacterial infection under a lifted nail — the green pigment (pyocyanin) is produced by the bacteria. This typically develops when moisture accumulates under a chronically detached nail plate. Pseudomonas nail infection requires treatment with an antiseptic (dilute bleach solution soaks, topical ciprofloxacin, or in some cases oral antibiotics). Brown or orange nails may indicate nicotine staining, contact with certain dyes or chemicals, or fungal infection. Blue or grey nails suggest medication effects (minocycline, antimalarials) or in rare cases systemic conditions causing nail discoloration from medications or pigment deposition.

Frequently Asked Questions

Don’t guess at toenail discoloration — get an accurate diagnosis. Contact Balance Foot & Ankle to schedule an evaluation with Dr. Biernacki in Southeast Michigan.

When Toenail Issues Become Medical Emergencies

Most toenail problems are cosmetic or mild — but a few warrant urgent podiatrist attention: any black streak that wasn’t caused by trauma (rule out subungual melanoma), rapidly spreading redness (cellulitis or paronychia), throbbing pain that wakes you at night (possible infection or ingrown nail), and any toenail issue in a diabetic patient. We see same-day appointments at Balance Foot & Ankle for these red flags.

For chronic fungus or thickening, FDA-cleared in-office laser treatment now achieves clear-nail rates of 70-80% with no oral medication side effects. Most patients see visible improvement within 6 months.

Frequently Asked Questions

How long does it take a toenail to grow back?

6-12 months for a full big toenail. Smaller toenails 4-6 months. Speed varies with age, circulation, and nutrition.

Will this affect other nails?

Trauma affects only the injured nail. Fungal infection can spread without treatment. Systemic causes affect multiple nails simultaneously.

Should I cover the nail or leave it open?

Cover with a breathable bandage during work or activity. Leave open at night for healing. Keep dry and clean.

In-Office Treatment at Balance Foot & Ankle

If home treatment isn’t providing relief for your toenail fungus, our podiatry team at Balance Foot & Ankle can help with same-day evaluations and advanced in-office care.