What should you know about itching under toenail?

Sweat, tight footwear, or a new polish or treatment can irritate the nail fold and nearby skin. A fungal nail infection may cause a nail to become thick, brittle, crumbly, yellowed, or separated from the nail bed; the surrounding skin can also itch or scale. Small injuries from pressure or impact may lift the nail and trap moisture beneath it. Eczema or contact dermatitis can affect the skin around the nail, while psoriasis can alter the nail surface and produce pits or separation. A dark mark after trauma should not be assumed to be dried blood without examination.

Because several nail conditions look alike, scraping, clipping, or removing the nail at home can make assessment harder and may injure the nail bed.

Wash and dry the foot carefully, including between the toes. Wear roomy shoes and change damp socks promptly. Keep the nail trimmed straight across without digging into the corners, and do not share clippers, socks, or footwear. Avoid picking under the nail or applying leftover steroid, antibiotic, or antifungal medicine; the wrong product can mask the appearance or irritate broken skin. A clinician or pharmacist can recommend an appropriate product after checking whether the problem is in the nail, the surrounding skin, or both.

Book an assessment if the itch lasts, the nail thickens or separates, several nails change, or the problem returns. Seek prompt care for increasing warmth, swelling, pus, severe pain, fever, or redness spreading from the toe. People with diabetes, reduced circulation, nerve damage, or a weakened immune system should arrange advice early for any foot or nail wound. A new or changing dark streak, pigment reaching the surrounding skin, or bleeding without a clear injury needs medical review.

Does the nail look infected, injured, inflamed, or separated? Would a nail sample clarify the cause before treatment? Should nearby skin be treated as well? How should I protect the toe in shoes, and what changes should prompt an earlier review?