Discover the Causes: Why Do Nails Become Thick and How to Treat Them

Nails get thick from aging, fungal infection, injury, or conditions like psoriasis. See a doctor if it persists.

Common causes

• Aging.
• Fungal infection (onychomycosis).
• Injury or trauma.
• Psoriasis.
• Poor circulation or diabetes.
• Ill-fitting shoes.

Treatment

• Antifungal medicine.
• Trim carefully.
• Keep feet clean and dry.

See a doctor

If thickening is painful, discolored or you have diabetes.

Prevention

Wear breathable shoes.

Fungal infection

Onychomycosis is the most common cause of thick, discolored nails, particularly toenails. It affects about 10% of the population, and up to 50% of people over 70. The nail turns yellow, brown or white, crumbles and becomes brittle.

Trauma

Repeated pressure from tight shoes or running can thicken toenails. A previous injury can lead to a deformed nail.

Age

Nails grow slower and become thicker and more brittle with age.

Psoriasis

Nail psoriasis causes pitting, thickening, discoloration and separation from the nail bed. It affects up to 50% of people with psoriasis.

Other causes

• Eczema.
• Lichen planus.
• Poor circulation and diabetes.
• Thyroid conditions.
• Yellow nail syndrome, a rare condition.
• Onychogryphosis (ram’s horn nails) in older adults.
• Medications.

Treatment

• Antifungal treatments: oral terbinafine (about 12 weeks for toenails), which has a cure rate of 70% to 80%, and itraconazole. Topical treatments such as efinaconazole and ciclopirox have lower cure rates, around 15% to 20%.
• Laser treatment has limited evidence.
• Nail removal in severe cases.
• For psoriasis: topical steroids, injections or systemic therapy.
• Trim and file thick nails regularly.

Regrowth

Toenails take 12 to 18 months to fully grow out.

See a doctor if

Nails are painful, change color suddenly, have dark streaks (which can indicate melanoma), or you have diabetes or circulation issues. A lab test can confirm fungus before treatment.

Prevention

Keep feet dry, wear breathable shoes, don’t share nail tools, wear sandals in public showers and cut nails straight across.

Fungus and other causes of thickening

Thick nails (onychauxis or onychomycosis) are most often caused by fungal infection, which affects roughly 10 percent of the population and up to 20 percent of people over 60, according to the American Academy of Dermatology. Other causes include repeated injury from tight shoes or sports, psoriasis, aging, poor circulation and conditions such as diabetes. Fungal nails often turn yellow, brittle and crumbly.

Treatment timeline

Nails grow slowly: about 3 mm a month for fingernails and 1 mm a month for toenails, so a toenail can take 12 to 18 months to regrow fully. Prescription oral terbinafine has cure rates of around 70 percent in trials but requires liver monitoring, while topical treatments such as efinaconazole work less often. Keep nails trimmed, dry and clean, and wear breathable shoes. See a doctor if there is pain, discoloration under the nail, or if you have diabetes.

Based on data from the American Academy of Dermatology and the Mayo Clinic