Mosaic warts are a type of plantar wart that grows in clusters on the bottom of your feet. Doctors also call this type of wart recalcitrant plantar warts or verrucae.

While some mosaic warts go away on their own, others are harder to treat and may require a doctor’s intervention.

Mosaic warts specifically appear on the bottom side of your foot. Doctors call this side the plantar side of the foot. Sometimes a person may only have one wart on the bottom of their foot. This is a solitary wart.

When the warts on the bottom of the foot appear in a cluster, they are mosaic warts. Other signs and symptoms include:

  • Thicker skin. Sometimes you may mistake your mosaic wart for a callus on the bottom of the foot.
  • Pain, especially when walking and standing.
  • Small black dots that appear on the warts. These are tiny blood vessels that have burst on the underside of the foot.

Mosaic warts can look like a corn. Sometimes a doctor must pare or file down the affected area to determine if it is a corn or mosaic warts.

Because these warts grow deeply into the skin, they can be very painful. This is especially true when you walk and put pressure on them.

Mosaic warts will typically go away without treatment, but it can take several months to years for this to happen. Most people decide whether to treat their warts based on if they’re causing them pain.

Treating mosaic warts can be uncomfortable because they’re on the bottom of the foot and it’s difficult to keep weight and pressure off after treatment.

Also, wart treatment can cause scarring. Your doctor should talk about risks and benefits before recommending treatments.

Here are seven of the most common treatments for removing mosaic warts:

1. Salicylic acid applications

Salicylic acid applications are available as over-the-counter medications at drugstores. There are also higher concentrations of salicylic acid solution for treating warts on the bottom of the foot, where skin can be quite thick.

The treatment works by exfoliating dead layers of skin from the warts, as well as triggering the immune system to fight off the virus.

Here are some tips for treating mosaic warts with salicylic acid:

  • Start by soaking the feet in warm water.
  • Use an emery board or pumice stone to file the outer layers of skin.
  • Apply the salicylic acid liquid or “sticky disc” to the wart, usually before bedtime.

2. Cryotherapy or ‘freezing’ warts

Cryotherapy is an approach that involves a doctor “freezing” a wart by exposing it to liquid nitrogen. This can cause warts to blister and fall off.

Cryotherapy can be painful if the mosaic warts are very deep. Sometimes a doctor may need to apply this treatment more than once.

According to the U.S. National Library of Medicine, cryotherapy can be effective in treating warts on the hands, but hasn’t been shown to be as effective in reducing warts on the feet because they are sometimes pushed inward.

3. Topical prescriptions

Doctors may prescribe topical treatments if salicylic acid doesn’t work well. Examples of these treatments include topical 5-fluorouracil (Efudex) or imiquimod (Aldara).

4. Injections

A doctor can inject some medications into the mosaic warts to help reduce them. Examples include bleomycin sulfate, Candida antigen, or interferon-alpha. These injections can trigger immune system response to help fight HPV, but they won’t cure the virus.

5. Oral medications

A doctor may prescribe oral medications to treat mosaic warts. One example is cimetidine, a medication usually prescribed to reduce the symptoms of gastroesophageal reflux disease (GERD). Other treatments may include oral retinoids or the dietary supplement diindolylmethane.

6. Laser therapies

Laser therapies, or laser surgery such as pulsed dye laser or Nd:YAG lasers, may be used to treat wart tissue. Laser therapies for wart removal work similarly to laser treatment for reducing scars. They focus on removing the upper layers of skin.

7. Surgery

Sometimes mosaic warts can linger and cause discomfort for years. When this is the case, a doctor may recommend surgical removal. This approach can be painful and cause scarring.

The human papillomavirus (HPV) causes mosaic warts. The virus infects cells in the skin known as keratinocytes. As a result, the skin gets thicker and tougher, creating a wart or warts.

A person can get HPV through direct contact with a person who has it or by touching contaminated surfaces. Examples include bare feet touching a contaminated shower floor or swimming pool. The virus enters through small breaks in the skin. Moisture makes the virus easier to enter.

You can treat your mosaic warts at home and reduce symptoms by taking the following steps:

  • Wearing comfortable shoes that have padding in the sole.
  • Purchasing special pads designed for plantar warts (usually available at a drugstore) that reduce pressure on the feet.
  • Refraining from sharing shoes, socks, or other footwear-related items with other people.
  • Covering mosaic warts with special waterproof bandages to keep from transmitting the virus that spreads the warts to other people.
  • Filing the wart using an emery board or pumice stone, usually after soaking the skin in the bath or shower. Always carefully dispose of any skin filings in the trash. Never share your emery boards or pumice stones.

Your primary care physician may recommend initial treatments for mosaic warts. If your warts are especially hard to treat, they may refer you to a foot specialist known as a podiatrist.

Mosaic warts can be difficult — but not impossible — to treat on the bottom of your feet. Time and repeated effort to treat the warts can help. Most mosaic warts will go away on their own with time.