A wart is a benign skin growth caused by an infection with the human papillomavirus (HPV), which stimulates the rapid growth of skin cells. Warts occurring under the toenail are known as subungual warts, while those around the nail plate are called periungual warts. These growths can present as nodular lesions that lift the nail plate or linear growths that penetrate beneath it. The location of these warts under the hard structure of the nail makes them uniquely challenging to treat effectively.
Why Warts Under the Toenail Are Difficult to Treat
The location of a subungual wart creates significant anatomical challenges for removal therapies. The main barrier is the hard, thick structure of the toenail plate, which shields the wart tissue underneath. This layer prevents topical treatments from reaching the infected cells with sufficient concentration to be effective.
Warts in this area are often deeply seated, growing into the sensitive nail bed and potentially affecting the nail matrix, which is responsible for nail growth. Aggressive treatment risks permanent damage to the nail matrix, potentially leading to long-term nail deformity or loss. Subungual warts can also be painful due to the pressure exerted by the growth under the rigid nail. Unlike common warts, subungual warts rarely resolve spontaneously, making intervention necessary.
Over the Counter Removal Methods
Salicylic acid preparations are the most common over-the-counter treatment for warts, working by slowly dissolving the infected skin cells. These products are available in various forms, such as liquids, gels, or patches. For the keratolytic agent to penetrate the thick nail and reach the wart, the affected area must be soaked in warm water and the overlying nail or dead skin gently filed down.
Patients must apply the treatment daily for several weeks, often up to 12 weeks, for success. Over-the-counter cryotherapy kits use a freezing spray to destroy the tissue by rapidly cooling it. However, these home-use sprays often fail to reach the necessary temperature or depth to fully treat a deep subungual wart.
The physical barrier of the nail plate severely limits the efficacy of both salicylic acid and home freezing. Aggressive self-treatment, such as excessive filing or cutting, should be avoided as it increases the risk of introducing bacteria and causing a secondary infection. If a wart persists after 12 weeks of consistent home treatment, or if it causes significant pain or nail deformation, professional medical attention should be sought.
Clinical Treatments Performed by a Professional
When over-the-counter methods fail, a healthcare professional can employ more intensive therapies to eradicate the deep-seated wart tissue. Prescription-strength topical treatments are often the first step, using higher concentrations of acid or agents like cantharidin, which causes blistering to lift the wart away. Immunomodulators, such as 5-fluorouracil, may also be prescribed to interfere with the wart’s cell growth.
In-office cryotherapy involves the precise application of liquid nitrogen, which is significantly colder than home options, to freeze and destroy the wart. This procedure often requires thinning or partial removal of the toenail to ensure the liquid nitrogen reaches the subungual lesion effectively. Multiple sessions, spaced two to three weeks apart, are necessary to achieve complete resolution.
Laser treatments provide another effective method, particularly the pulsed dye laser (PDL) or the carbon dioxide (CO2) laser. The PDL targets the tiny blood vessels supplying the wart, causing the infected tissue to die from lack of blood flow. The CO2 laser works by precisely vaporizing the wart tissue layer by layer.
For large or persistent subungual warts that have not responded to other methods, surgical excision may be performed. This procedure involves scraping or cutting away the wart tissue. Temporary removal of the overlying nail plate is required to gain access to the wart on the nail bed.
Healing and Preventing Recurrence
Recovery time following professional treatment can be prolonged, especially after surgical excision or aggressive laser therapy. The wound created by removal must heal, and the toenail must regrow, which can take several months. If the treatment involved the nail matrix, there is a risk of temporary or permanent nail dystrophy, resulting in changes to the nail’s shape or texture.
Warts have a high rate of recurrence because the HPV virus is difficult to eliminate entirely. To help prevent the return of the wart, maintaining rigorous foot hygiene is important, including keeping the feet clean and dry, as the virus thrives in moist conditions.
Avoid walking barefoot in public, damp environments like locker rooms, communal showers, or pool decks, where the virus is easily transmitted. Do not share personal items such as towels, nail clippers, or shoes to limit viral spread. Regularly inspecting the feet for early signs of recurrence allows for faster and less invasive re-treatment.