Toenail Diseases — Types, Causes, Treatment & When to See a Podiatrist

✅ Medically reviewed by Dr. Thomas Biernacki, DPM — Board-Certified Podiatrist · Last updated April 7, 2026

Understanding Toenail Health

Your toenails are more than just cosmetic — they’re windows into your overall health. Made of a tough protein called keratin, healthy toenails grow about 1.6mm per month and should appear smooth, uniformly colored, and free of ridges or spots. When disease, infection, or injury disrupts the nail matrix (the growth center beneath the cuticle), it shows up as visible changes in the nail that can take 12–18 months to fully grow out.

At Balance Foot & Ankle, we treat the full spectrum of toenail conditions — from routine fungal infections to complex nail pathology. Understanding what’s causing your toenail changes is the first step toward effective treatment and, in some cases, catching systemic health conditions early.

Fungal Toenail Infections (Onychomycosis)

Fungal toenail infection is by far the most common toenail disease, affecting roughly 10% of the general population and up to 50% of adults over 70. The infection is caused by dermatophyte fungi that thrive in warm, moist environments — shoes, socks, locker rooms, and showers. The fungus invades beneath the nail plate, causing gradual thickening, yellowing, crumbling, and separation of the nail from the nail bed.

Onychomycosis typically starts as a white or yellow spot near the tip of the nail and progressively spreads toward the cuticle. The big toenail is most commonly affected. Risk factors include diabetes, peripheral vascular disease, immune suppression, aging, athlete’s foot, and nail trauma. Without treatment, the infection rarely resolves on its own and often spreads to adjacent nails. For comprehensive treatment guidance, see our detailed guide on toenail fungus treatment.

Ingrown Toenails (Onychocryptosis)

Ingrown toenails develop when the edge or corner of a toenail grows into the surrounding skin, causing pain, redness, swelling, and sometimes infection. The big toe is almost always affected. Common causes include improper nail trimming (cutting too short or rounding the corners), tight shoes, genetic nail shape (overly curved nails), and toe trauma.

Mild ingrown nails may respond to warm soaks and proper trimming, but infected or recurrent ingrown nails typically require professional treatment. A partial nail avulsion — removing the offending nail border under local anesthesia — resolves the problem immediately. When combined with phenol matrixectomy (permanently narrowing the nail), the recurrence rate drops below 5%. Learn more about ingrown toenail treatment.

Thickened Toenails (Onychauxis & Onychogryphosis)

Thickened toenails are extremely common, especially in older adults. Onychauxis refers to uniform nail thickening, while onychogryphosis (ram’s horn nail) describes severely thickened, curved nails that can become almost claw-like. Common causes include repeated microtrauma (from tight shoes or athletic activity), fungal infection, poor circulation, psoriasis, and age-related changes to the nail matrix.

Thickened nails are difficult to trim at home and can cause pain from shoe pressure. Professional podiatric nail care — using specialized instruments to safely reduce nail thickness — provides immediate comfort. If fungal infection is the underlying cause, treating the infection can gradually restore normal nail growth.

Discolored Toenails — What Each Color Means

Toenail color changes are one of the most common reasons patients visit our office. Here’s what different colors typically indicate: yellow nails are most often caused by fungal infection, though nail polish staining and psoriasis can also cause yellowing. White spots or patches (leukonychia) are usually from minor nail trauma but can indicate fungal infection if they spread. Brown or black discoloration may be a subungual hematoma (blood under the nail), melanonychia, or rarely subungual melanoma. Green nails typically indicate a Pseudomonas bacterial infection. Blue nails can signal circulatory problems or oxygen deficiency.

For more on dark spots specifically, see our guide on black spots under the toenail.

Nail Psoriasis

Up to 80% of people with psoriasis will develop nail changes at some point. Psoriatic nail disease can look remarkably similar to fungal infection — thickening, yellowing, crumbling, and nail bed separation (onycholysis). Distinguishing features include tiny pits (small depressions in the nail surface), oil drop sign (salmon-colored patches visible through the nail), and splinter hemorrhages (tiny lines of blood under the nail).

Nail psoriasis can also occur without skin psoriasis, making diagnosis challenging. Treatment may include topical steroids, vitamin D analogs, or in severe cases, systemic medications prescribed in coordination with a dermatologist.

Nail Trauma & Subungual Hematoma

Dropping something heavy on your toe or stubbing it forcefully can damage the nail matrix and cause blood to pool beneath the nail plate (subungual hematoma). The nail turns dark purple or black, and pressure from the trapped blood can be extremely painful. If the hematoma covers more than 25% of the nail, draining it (trephination) provides immediate relief.

Repetitive microtrauma — from running, hiking, or wearing shoes that are too short — can cause chronic nail damage, thickening, and eventual nail loss (onycholysis). Runners frequently experience “runner’s toe” or “black toenail” from the nail repeatedly hitting the front of the shoe. Ensuring a thumb’s width of space between your longest toe and the end of the shoe helps prevent this.

Melanonychia — When a Dark Streak Needs Attention

Melanonychia is a dark longitudinal streak running from the cuticle to the tip of the nail, caused by increased melanin production in the nail matrix. In many cases it’s benign — particularly in people with darker skin tones, where it’s a normal variant. However, melanonychia can also be an early sign of subungual melanoma, a rare but serious form of skin cancer.

Warning signs that warrant urgent evaluation include a new streak appearing in only one nail (especially in lighter-skinned individuals), a streak that’s widening over time, irregular or blurred borders, pigment extending onto the cuticle or surrounding skin (Hutchinson’s sign), and nail dystrophy or destruction. Any new dark streak in a single toenail should be evaluated by a podiatrist or dermatologist.

Treatment Options for Toenail Diseases

Professional Treatments

At Balance Foot & Ankle, we offer a full range of toenail treatments. For fungal infections, options include oral antifungal medication (terbinafine or itraconazole), topical prescription antifungals (efinaconazole, tavaborole), laser nail therapy, and in severe cases temporary nail removal to allow direct treatment of the nail bed. Ingrown nails are treated with partial nail avulsion with optional permanent matrixectomy. Thickened nails are professionally debrided for comfort and cosmetic improvement.

At-Home Care

For mild fungal infections, OTC antifungal treatments can be used as adjunct therapy. Keep nails trimmed straight across, not too short, and avoid rounding the corners. Wear moisture-wicking socks and breathable shoes. Disinfect nail clippers after each use, and never share nail tools. Apply antifungal powder or spray inside shoes regularly.

Home Care & Prevention

Good nail hygiene prevents the majority of toenail problems. Trim nails straight across using clean, sharp nail clippers — avoid cutting into the corners. Keep feet clean and dry, changing socks daily and rotating shoes to allow them to air out. Wear shower shoes in public pools, gyms, and locker rooms. Moisturize the cuticle area but avoid pushing cuticles back aggressively.

For diabetic patients, daily foot and nail inspection is essential. Diabetic neuropathy can mask pain from ingrown nails or infections, allowing problems to escalate without symptoms. If you have diabetes, schedule regular podiatric nail care rather than attempting to manage thick or problem nails at home.

Frequently Asked Questions

Can toenail fungus spread to other nails?

Yes — fungal infections commonly spread from one nail to adjacent nails, and can also spread to the skin (athlete’s foot) or to other people through shared surfaces. Treating the infection early and maintaining good hygiene helps prevent spread.

How long does it take for a toenail to grow back?

A complete toenail takes approximately 12–18 months to grow from the matrix to the tip. This is why toenail treatments — especially for fungal infections — require patience. You won’t see a fully clear nail until the new growth has completely replaced the old damaged nail.

Is it normal for toenails to get thicker with age?

Some thickening is normal as we age due to reduced blood circulation and slower nail growth. However, significant thickening is often caused by fungal infection, repeated trauma, or underlying conditions — not just aging. Professional evaluation can distinguish normal age-related changes from treatable conditions.

Should I be worried about a dark line on my toenail?

A single dark longitudinal streak — especially if it’s new, widening, or in a lighter-skinned individual — should always be evaluated by a podiatrist or dermatologist. While most are benign, a small percentage represent subungual melanoma, which has the best outcomes when caught early.

Clinical References

1. Baran R, Dawber RPR. Diseases of the Nails and their Management. 4th ed. Wiley-Blackwell. 2012.
2. Rich P. Nail disorders: diagnosis and treatment of infectious, inflammatory, and neoplastic nail conditions. Medical Clinics of North America. 2013;97(4):659-672.
3. De Berker D. Clinical practice: fungal nail disease. New England Journal of Medicine. 2009;360(20):2108-2116.