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What kind of acid does the podiatrist use on warts?

Warts are a common skin condition caused by the human papillomavirus (HPV). They typically appear on the hands and feet as small, rough, raised bumps. While warts often go away on their own, many people seek treatment from a podiatrist to remove stubborn plantar warts on the feet. Podiatrists have several methods available to treat warts, some of which utilize acids.

Common Types of Warts Treated by Podiatrists

The most common types of warts on the feet that podiatrists treat include:

  • Plantar warts – Occur on the soles of the feet. They grow inward, causing pain and discomfort when walking.
  • Mosaic warts – Clustered group of plantar warts that grow together.
  • Periungual warts – Develop around the nails, often under the nail bed.

Plantar warts are the most bothersome type as they can make standing and walking painful. They look like calluses with small black pinpoints, which are actually clotted blood vessels. Mosaic warts occur as a group of plantar warts fused together in a patch. Periungual warts grow under and around the toenails, sometimes causing ingrown nails. Podiatrists have specialized tools and treatments to remove these troublesome warts on the feet.

Salicylic Acid

One of the most common wart removal methods used by podiatrists is salicylic acid. Salicylic acid is a beta hydroxy acid that sloughs off the outer layers of dead skin cells. By removing the thick layer of hard skin overlying a wart, the salicylic acid can penetrate deeper to attack the root of the wart.

Salicylic acid treatments come in several forms, including:

  • Plasters – Small medicated adhesive pads that stick directly on top of a wart. These provide continuous acid exposure to that specific area and are convenient for wart removal on the feet.
  • Liquids – Bottled solutions that are brushed or dripped onto warts. These tend to be messier than plasters when treating feet.
  • Gels – Thicker gels are also applied directly to warts. The thicker consistency helps the acid stay in contact with the wart rather than rubbing off on socks or shoes.

The podiatrist will have the patient apply the salicylic acid treatment at home on a regular schedule, usually daily. After several weeks of application, the dead wart tissue will detach from the deeper layer of skin and fall off. Continued use is often needed to fully eliminate very stubborn warts on the feet.


Cantharidin is a topical blistering agent derived from beetles. When applied to warts, it causes irritation and blistering of the outer skin layers over the wart. After this blistered skin peels away, it exposes the wart underneath so stronger treatments can penetrate. Due to its blistering properties, cantharidin is typically only applied by the podiatrist in the office.

The steps for cantharidin wart removal are:

  1. Clean and dry the foot and wart thoroughly.
  2. Apply petroleum jelly around (but not on) the wart to protect the healthy surrounding skin.
  3. Use a tiny brush or cotton swab to paint a layer of cantharidin only on the wart.
  4. Allow the cantharidin to dry completely.
  5. Cover with a bandage.
  6. After 6-24 hours, wash off the blistered skin that forms.
  7. Repeat the procedure every 2-6 weeks until the wart is gone.

The irritation caused prompts an immune reaction against the virus in the wart. Cantharidin is effective for resistant plantar warts on the feet but the blistering effect causes temporary pain that may limit activity.

Trichloroacetic Acid

Trichloroacetic acid (TCA) is a caustic chemical solution used by podiatrists to cauterize and destroy wart tissue. It is typically applied in higher concentrations of 50-90% to treat plantar warts on the feet.

The podiatrist takes the following steps when using trichloroacetic acid on warts:

  1. File down thick calluses overlying the wart to expose the deeper tissue.
  2. Swab TCA directly onto only the wart using a cotton-tip applicator or specialty applicator.
  3. Allow the area to dry completely until a white frosting develops on the treated area. This indicates the acid has penetrated through all layers of the wart.
  4. Apply petroleum jelly to protect surrounding skin.
  5. Repeat weekly until the wart falls off naturally, usually within 1-2 weeks.

The acid essentially cauterizes the tissues of the wart, prompting shedding of the dead cells and triggering increased blood flow to carry away debris. The high acid concentrations can be painful initially so petroleum jelly helps minimize irritation of nearby healthy skin.

Benefits of Using Acids for Wart Removal

Acids offer some advantages when used properly to remove warts on the feet:

  • Effective: Salicylic, cantharidin, and trichloroacetic acid can successfully remove even stubborn plantar warts on the bottom of the feet.
  • Convenient: Salicylic acid treatments are easy for patients to use at home on their own schedule.
  • Lower cost: Acid treatments are more affordable compared to other in-office procedures.
  • Non-scarring: The acids selectively remove wart tissue without scarring healthy skin when applied properly.
  • Painless: Salicylic acid and cantharidin are relatively painless compared to other destructive treatments.

Using acids allows podiatrists to gradually break down the thick, hardened layers of a wart for more effective penetration. The milder acids like salicylic acid and cantharidin also cause less risk of pain, scarring, or nerve damage compared to aggressive wart removal techniques.

Potential Side Effects and Risks

While generally safe for wart removal when used correctly, acids do carry some potential side effects and risks:

  • Skin irritation: Can cause redness, stinging, burning, and peeling of healthy skin around the wart.
  • Incomplete removal: May not fully destroy the root of deeper warts which can lead to recurrence.
  • Scarring: Higher risk of scarring if the acid inadvertently spreads onto too much healthy tissue.
  • Pain: High concentrations of salicylic or trichloroacetic acid can damage nerves leading to increased pain.
  • Healing complications: Delayed wound healing if the acid damages new skin cells trying to form over the treated area.

Using petroleum jelly as a protectant barrier and carefully applying acid only to the wart itself minimizes potential risks and side effects. Podiatrists also avoid using acids on certain areas of the foot such as joints or bony prominences where it may be absorbed more deeply. Clinical monitoring is important to change methods if the acids are not fully eliminating the stubborn warts.

Other Wart Removal Options

While acids are a mainstay of plantar wart treatment, podiatrists may use other modalities as well. Additional in-office options include:

  • Cryotherapy: Freezing warts with liquid nitrogen to rupture their cell walls.
  • Electrodesiccation: Burning off warts with an electrical current.
  • Laser: Using focused light energy to vaporize and destroy wart tissue.
  • Surgical excision: Cutting away warts and a border of healthy tissue using a scalpel, scissors, or razor blade.
  • Curettage: Scraping away warts using a special spoon-shaped instrument.

Podiatrists may also prescribe prescription-strength medications including:

  • Retinoids: Creams like tretinoin (Retin-A, Altinac, Tretin-X) derived from vitamin A that remove outer skin layers.
  • Imiquimod cream: Boosts immune activity against wart virus to help clear lesions.
  • Interferon injections: Injections of a natural protein that stimulate the immune response against warts.
  • Bleomycin injections: Injection of an anticancer drug that damages wart tissue.
  • Dinitrochlorobenzene (DNCB): Chemical applied to the skin to create an allergic reaction targeting warts.

Podiatrists may use combinations of salicylic acid along with cryotherapy, laser treatments, or curettage for a more aggressive approach against troublesome plantar warts on the feet.

Home Treatments to Use With Acids

In addition to in-office acid treatments, podiatrists often recommend patients perform home therapies between appointments. These include:

  • Soaking the feet in warm water to soften and loosen thick calluses over warts.
  • Using a pumice stone, callus shaver, or foot file to help peel away dead skin.
  • Applying moisturizer daily to keep calluses from becoming too dry and painful.
  • Covering warts with adhesive tape or bandages after acid application to increase penetration.
  • Avoiding picking at warts as this can spread the virus and cause bleeding.

Keep the feet protected with clean, dry socks and avoid direct skin-to-skin contact with warts. Replace toothbrushes frequently to avoid reinfection if patients have warts around the mouth. Diligent at-home care combined with in-office acid treatments offers the best chance of successfully eliminating plantar warts.


Salicylic acid, cantharidin, and trichloroacetic acid are common choices for podiatrists removing stubborn plantar warts from patients’ feet. These acids have the advantage of being lower cost and convenient compared to other in-office treatments. Careful application preserves healthy tissue while the acids penetrate down to destroy the root of warts. Using acids in combination with other modalities boosts success for eliminating even resistant warts on the feet. With proper use, acids provide a safe and effective way for podiatrists to remove one of the most common foot problems.

Acid Treatment Description Advantages Disadvantages
Salicylic Acid Keratolytic beta hydroxy acid that causes peeling of outer skin layers overlying wart.
  • Convenient at-home use
  • Low cost
  • Typically painless
  • May require weeks of treatment
  • Can irritate healthy skin
  • Doesn’t always fully destroy wart root
Cantharidin Topical blistering agent derived from beetles.
  • Promptly creates blistering of outer wart layers
  • Low pain
  • Multiple in-office visits needed
  • Temporary pain from blistering
Trichloroacetic Acid Caustic acid that cauterizes and destroys wart tissue.
  • Effective for resistant warts
  • Low cost
  • Can be painful initially
  • Higher risk of scarring if applied improperly

When to Seek Further Treatment

While acids typically resolve most warts, consult your podiatrist promptly if:

  • The wart does not improve despite weeks of acid treatment.
  • The wart bleeds excessively when debriding calluses at home.
  • Signs of infection develop like increasing pain, redness, warmth or pus.
  • New warts continue to develop in the surrounding area.
  • The wart interferes with walking or normal activities.

In recalcitrant cases, podiatrists can utilize cryotherapy, laser ablation, curettage, or surgical excision to remove warts. They may also prescribe stronger medicated creams, immunotherapies, or perform a biopsy to rule out cancer for atypical or rapidly growing lesions. While acids commonly resolve warts successfully, podiatrists have additional options to eliminate warts refractory to initial treatments.

Preventing Transmission of Wart Virus

To avoid spreading warts on the feet:

  • Avoid direct contact between warts and other people’s skin.
  • Wear shower shoes in public areas like gyms and pools.
  • Disinfect pedicure tools before reusing on multiple people.
  • Change socks daily.
  • Avoid biting or picking at fingers around mouth warts.
  • Request family members not share bedding, towels, or shoes with affected individuals.
  • Keep feet covered with shoes or socks around the house if living with someone having plantar warts.

HPV thrives in warm, damp environments like pools, showers, and locker rooms. Warts may spontaneously resolve after 1-2 years, but diligent hygiene minimizes spread during this time. Get all household members evaluated as virus can persist on surfaces and infect previously normal skin.

The Takeaway

Salicylic acid, cantharidin, and trichloroacetic acid offer a simple, low-cost way for podiatrists to gradually break down and destroy thick plantar warts. Careful application preserves normal skin while exposing the roots of warts to the acidic effects. Combine acids with cryotherapy, laser, or surgical treatments for more extensive warts. Supportive home care like moisturizing and callus removal enhance acid penetration into warts between in-office treatments. Seek further podiatric care if over-the-counter acids do not resolve warts after 3 months of use or if signs of complications develop.