What is medical nail avulsion?
Medical nail avulsion is the removal of a fingernail or, more often, a toenail by chemical destruction of the nail plate. It is a painless process that takes several weeks to complete.
Nails can also be partly or completely removed by:
- Surgical nail avulsion
These more aggressive processes are painful and may lead to permanent nail dystrophy.
Who gets medical nail avulsion?
Medical nail avulsion is used to remove a nail that is causing symptoms that have not improved by other means. Examples include:
- Complete nail destruction due to fungal infection
- Thickened nail (onychogryphosis) due to any cause, eg congenital, ageing, tight shoes, psoriasis
- Ingrown nail (onychocryptosis).
What chemical is used for medical nail avulsion?
The main ingredient of a medical nail avulsion preparation is 40% urea. The urea is compounded with various other ingredients to make a suitable formulation that slowly macerates the nail plate. A typical 30-g formulation used for chemical nail avulsion is listed here.
- Urea 40%
- White wax 5%
- Anhydrous lanolin 20%
- White petrolatum 35%
Urea is also used in a lower concentration to remove scale and soften dry skin.
How is medical nail avulsion undertaken?
- Clip back and pare down the nail so it is as short and thin as possible
- Protect surrounding skin: apply tincture of benzoin then zinc oxide tape to the nail folds
- Apply the urea preparation to exposed nail and bed
- Cover with occlusive tape dressing
- Keep the treated area clean and dry
In one week, remove the occlusive tape dressing, gently pare away the soft tissue, wash the digit and nail using an antiseptic or saline, and repeat steps 1 to 4 above.
Once all the diseased or thickened nail plate has been removed after 3 to 6 weeks, the dressings can be removed and the chemical nail avulsion has been completed. Protect the nail bed from injury, especially initially. A protective layer of skin will grow over the nailbed within a few weeks.
Complications of medical nail avulsion
Secondary bacterial infection is the main risk, but is uncommon.
Allergic contact dermatitis may arise due to the use of tincture of benzoin, which contains the allergen balsam of Peru, and zinc oxide tape, which contains the allergen colophony/rosin. In this case, alternative adhesive preparations may be used.
What is the outlook for medical nail avulsion?
Medical nail avulsion is not completely successful at curing fungal nail infection, as fungi may be growing in the nail matrix under the proximal nail fold. This will be obvious as the nail begins to grow out again. Nor is it effective treatment for an inflammatory nail disease such as psoriasis.
In a healthy young adult, regrowth of a fingernail is expected to take around 9 months. It takes about 18 months to fully grow a great toenail. Nail growth may be slower in older individuals or in people with poor circulation.
The process can be repeated at a later date if desired.