What should you know about thick under toenail?

Fungal nail disease can make the nail thicker, crumbly, discoloured, or partly detached from the nail bed. Tight footwear and repeated impact can also change the nail after an injury. Nail psoriasis may cause ridges, pits, lifting, or a build-up beneath the nail. The appearance alone cannot reliably separate these causes.

A clinician may inspect the nail and surrounding skin, ask whether other nails are involved, and take a nail sample when confirmation would change treatment. Athlete’s foot can coexist with fungal nail disease and may need attention as well.

Keep feet clean and dry, change socks when damp, and choose shoes with enough room for the toes. Trim the nail straight across after softening it, and do not dig under it or share clippers. Avoid covering a suspected infection with cosmetic polish until it has been assessed.

Treatment depends on the cause and how much of the nail is affected. Options may include a prescribed nail medicine, [Oral Antifungal Treatment](/treatments/medical-dermatology/oral-antifungal-therapy/), or selected devices such as [Laser Treatment For Nail Fungus](/treatments/laser-and-energy/laser-nail-fungus-treatment/).

Arrange a dermatology review if the thickening persists, spreads to other nails, causes pain in shoes, or keeps returning. Seek prompt care for redness, warmth, swelling, drainage, a rapidly changing dark area, or an unexplained nail that lifts. People with diabetes, reduced circulation, nerve problems, or a weakened immune system should have foot changes assessed early.

Ask whether the nail needs a fungal test, whether nearby skin suggests athlete’s foot, and which treatments fit your medicines and health history. You can also ask how to trim the nail safely and how long healthy nail growth may take to replace the damaged portion.