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Plantar Warts Are Pain In The Neck – Here is everything you need to know about them!

Ask any practitioner and many of them say treating warts can be frustrating for both the practitioner and the patient. Why? This is because any mode of treatment we choose, there is a good chance of failures or recurrences, and there is no gold standard treatment for warts.

If you have plantar wart, I highly recommend that you read the entire article, but if you don’t have time, at least go to the section for available treatments. This is crucial for patients to understand the different types of treatments, and their adverse effects, expected outcome (prognosis) and cost. 

In chiropody/podiatry settings, we see patients with plantar warts on a daily basis. But not all warts are easy to treat, especially if the wart has been there for more than 2 years. Warts are usually harmless and can disappear without treatment within the first few months. But they can also cause some levels of discomfort, pain, and cosmetic concerns. After all, the wart is an infection and needs to be treated.

Plantar wart (verruca pedis) is a skin infection caused by Human Papillomavirus (HPV) and passes between people through direct contact to the viral particles (skin-to-skin contact), but can be also transmitted by indirect contact such as  walking barefoot on contaminated surfaces (public areas including locker rooms, shower, gym, etc.), socks, shoes, towels and sport equipment. Some activities such as picking at warts with fingernails or objects such as nail clipper or pumice stone can also result in transference of infection to hands or other parts of the body. Patients should be encouraged to wear proper foot coverings like shower
shoes or sandals when walking on possibly contaminated surfaces in public areas
to avoid any direct skin contact. Any item that comes into contact with a wart
should be thoroughly washed with hot water and soap.  If you have a plantar wart, it is a good idea to cover it with tape, or “verruca socks”, and pool-side sandals if you go to public area such as swimming pool. Moreover, simple domestic hygiene such as cleaning the baths or showers after use and avoiding shared towel or socks are important to reduce the risk of cross contamination. If the wart is under or around the nails, biting the nails must be avoided or the virus can easily cause oral wart infection.

It has been reported that Human papillomavirus can survive months to years on surfaces. The incidence increases during the school years to reach a peak in adolescence and early adulthood. There are over 150 types of HPV viruses (distinguished based on their DNA), of which only a few of them can cause plantar warts (and some other ones can cause genital, oral or anal warts). Each of these viruses behave differently to some degree, and they have different preferred sites of infection. For instance, HPV-1 replicates in more keratinized skin areas such as palms and soles, while HPV-16 prefers genital area.

To get a plantar wart, there should be some degree of skin impairment such as abrasion, cut or maceration (too much moist), so the virus can enter the skin and reach the stem cells at the basal membrane of the skin. That explains why swimming pools and shower rooms are a hotspot for getting a plantar wart as the skin becomes softer in contact with water and just a tiny hole can be a portal of entry for the virus. As the skin cells shed, viral particles are released and can be transmitted to surfaces where the virus will remain until picked up by a new host or spread to adjacent sites. That is why covering the wart(s) with a band aid (or duct tape) is a good idea to prevent its spread. 

Warts prefer a moist environment. Since it is more likely that the warts survive on sweaty feet, part of the treatment plan should be drying out the skin (by topicals such as Foot Fresh or Drysol).

Warts at the bottom of the feet (plantar wart) are usually more refractory to the treatment than common warts and they often grow inward. Moreover, HPV knows how to survive by evading the host immune surveillance. Hence, there are different treatments and modalities available out there to fight the battle against these sneaky viruses. However, none of these treatments are no panacea (there is no guarantee in medical treatments anyway). Also, we should remember that the number of wart lesions does not affect the treatment outcome (prognosis). 

I call these viruses sneaky because most people do not have any idea how they got the virus, but the virus finds its way and resides inside the infected cells, sometimes for years. The viruses live as parasite and introduce their DNA into the normal skin cells to reproduce themselves and also be able to hide from the human immune system. That is why it is common that the wart can survive more than 6 months because it knows how to protect itself from the immune system. That explains the challenge in treating warts and also why immune compromised people have massive and usually resistant warts.

There is a clinical impression that warts in adults, especially in elderlies, are slower to clear with or without treatment. There are reports that warts are more likely to spontaneously disappear in children younger than 12 years old.

Some literature also categorizes the wart lesion as a benign tumor because of the similar mechanism of uncontrolled increase in cell growth and reproduction. That explains why there are some anti-cancer medications used for wart viruses such as Bleomycin and Fluorouracil (5FU). Some types of warts, mainly genital warts, can transform into cancer, but this is extremely rare in the foot. However, if you see a wart similar to the image below, don’t wait and see your physician or chiropodist immediately. 

Above is a verrucous carcinoma

How long is the incubation time?

You may wonder how long after the first contact, warts will show up. The answer is not clear but we know it ranges from few weeks to more than a year! (4 weeks to 20 months). 

What does a wart look like? How can we distinguish it from a corn?

Warts can manifest differently depending on the location, age, subtype of the virus, patient’s immune system etc. There are several clinical manifestations of the lesions but we should remember that not every wart has all of the following criteria:

  1. Black dots (present or not) (this one is diagnostic for warts)
  2. Impaired skin lines (dermatoglyphics) in the lesion (checked better with dermoscopy) 
  3. Arrangement (single or confluent)
  4. Level (Raised or flat)
  5. Aspect (Rough/lobed or smooth/not lobed)
  6. Border (usually sharply defined)
  7. White skin flakes (present or not)
  8. Color (Yellow or red)
  9. Overlying callus (present or not present)
  10. Pain or no pain

The small black dots are widely accepted to be the end of thrombosed (clotted) capillaries (small vessels) within the lesion. If you see these black dots in a lesion, it is most likely a wart.  

On the bottom of the foot, most plantar warts are beneath the pressure points such as ball of the foot, heels, tip of the toes (due to higher pressure and more possible damage to the skin). Individuals may have single or multiple lesions. Sometimes, small cluster of warts that almost look like vesicles (small blisters) may form around a large wart, and sometimes multiple warts merge and form a larger plaque of warts called mosaic wart. These warts are sometimes the most difficult ones to treat. 

What are the risk factors for Plantar Wart?

Major risk factors include having pre-existent warts, being in close contact with someone who has a pre-existent wart, walking barefoot, hyperhidrosis (sweaty feet), and compromised immune system. 

 

Do all warts look similar? 

There are different types of warts (based on their appearance) including common warts, plane wart, filiform or digitate warts, mosaic warts, periungual (around or under the nails) warts, Butchers’ warts (occupational handlers of meat, poultry or fish, mostly in the hands), and pigmented warts (mostly in Japanese people).

Above is a cluster of plantar warts

Mosaic warts: These warts are plaques formed by merging of closely grouped small warts and are one of the most stubborn ones caused by HPV type 2. Particularly, in immunocompromised patients mosaic warts can spread out and cover a large area on the bottom of the foot.

Above is a Mosaic Wart – Note the small black dots in the wart.
  
Above is a Mosaic wart in an immunocompromised patient.

Is there any immunity or vaccine for warts?

No, there is no immunity or vaccine for plantar warts. There are vaccines for other types of HPV infections (such as genitals) but not for plantar warts. We still do not fully understand why the immune system in a healthy person cannot get rid of the plantar warts. But the main theory says that the virus hides itself and its DNA inside the skin cells (epidermal cells) and that is why the immune system cannot recognize it. However, there are reports showing that a humoral immunity may be established by antibodies that can prevent future reinfection of that specific HPV subtype. 

Are warts painful?

It can be painless or painful depending on the location, the amount of callus, and the type of the wart. Many patients with plantar wart present with pain or the sensation of a pebble or swelling under their foot. But generally, pain is not a diagnostic symptom for warts.

What are the available wart treatments?

Success in wart treatment depends on multiple factors and each patient will respond differently. Therefore, the treatment should be individualized based on age, pain tolerance, commitment to the treatment, financial status, location of the wart and the duration of the infection. 

During the first appointment, different treatment options including their expected
outcome, adverse effects, degrees of pain, and cost will be explained to the patient. Then based on the clinical manifestation and location of the wart, age of the patient, their expectations, pain tolerance, neural and vascular condition of the foot, and financial status of the patient, the practitioner will design a treatment plan. 

Some practitioners prefer to monitor early warts in young children because these warts may spontaneously disappear within 2 years. However, not treating the wart can also allow the wart to persist longer and become more resistant. Usually, it is more difficult to treat a wart if it has been present for more than 6 months. Warts in adults are also more stubborn than in children. 

Below, I listed several treatment options, of which we can provide most of them at Orangeville Foot Clinic.

1- Occlusion:

There is no evidence-based research that suggests covering the warts cures them and is not suggested as a main treatment. However, covering the wart with an adhesive tape or a duct tape may be considered as a complementary remedy. 

Advantages: Covering the wart can reduce the risk of spreading. Low cost. No pain. Increases the efficacy of the main course of treatment. 

Disadvantages: Skin reaction to the adhesive. 

2- Salicylic Acid (and other types of acid treatments such as trichloroacetic acid):

It works by removing the keratin (outer layer of the skin) surface. Remember, warts hide in keratinocytes (cells full of keratin) and use them as source of nutrition. 

Advantages: Usually pain free during and after treatment unless the skin reacts and leads to contact dermatitis or blistering. Low cost. Safe to use at home. 

Disadvantages: Low success rate (39%). Takes weeks to months of daily applications, along with regular pairing (debridement) of the wart in the clinic. Not recommended for certain patients including patients with diabetes, peripheral neuropathy, and poor circulation as the acid can cause a wound. Prolonged treatment not recommended in children and pregnancy. Lower success rate in children younger than 12y. 

Before applying the acid, some suggest soaking in warm water for 5-10 minutes, then drying of the area before using a file, emery board or pumice stone to remove the thickness of the lesion. Then apply the acid and use a non-porous tape such as duct tape to occlude the lesion. 

One of the most (and challenging) parts of this treatment regimen is patient compliance. 

I usually suggest to mask the normal skin around the wart with nail polish or a cream like Polysporin before applying the acid compound. 

3- Cryotherapy:

Freezing the wart off with liquid nitrogen is traditionally one of the most common routes of treatment in doctor’s office. But it is not always the best choice of treatment. Overall success rate is less than 50%. There are reports saying it is less effective than Salicylic Acid. It has been said that freezing works by stimulating the immune system. 

Advantages: Relatively low cost, 65% success rate on HPV type 1 (HPV-1).

Disadvantages: Painful during and after the treatment, the pain is unpredictable and variable between patients, needs several appointments in the clinic, more effective for warts on hand than feet, limited control on how deep the normal tissue under and around the wart will be damaged, requires regular wart paring (debridement), high rates of failure or recurrence, not recommended in patients with poor circulation, Raynaud’s or peripheral neuropathy. Can leave a scar and/or cause a blister. Because of the pain, this form of treatment is not recommended for young children. 

Treatment is repeated every 2 to 3 weeks for up to 3 months. Double-freeze therapy is a technique in which the warts are frozen until a 1-2-mm ice halo forms and then fully thawed, then immediately refrozen again. This has been said to increase the efficacy of the treatment but can be very painful. This treatment should be avoided if the wart is on nail matrix, or superficial nerves such as sides of the toes, or over a bony prominence.

Liquid Nitrogen used for this technique should have a temperature of -196 ̊C. Over the counter products such as Verruca Freeze only freeze the tissue to -70 ̊C and are even less effective.

4- Canthacur (cantharides “κανθαρίδες” in greek means beetle)

Hycleus lugens, a colored beetle, that secretes cantharidin and that is why this treatment is called “Beetle Juice”

This is one of the most popular wart treatment options in our office. 

Medications made from blistering beetles goes back to ancient times. It has been used for wart treatment since 1950. Cantharidin (Canthacur) is a vesicant (blistering) topical that lysis the keratinocytes (outer layer of skin) where the wart viruses are residing. 

The blister usually occurs 24-48 hours after application, but sometimes pain starts even earlier. It can cause a blood blister (dark blister) which is normal. 

There are several systematic reviews and researches that found topical cantharidin alone led to significant clearance of warts, especially when mixed with Podophyllin and salicylic acid. This mixture is available as Canthacur Plus or Canthacur PS which is stronger than regular cantharidin. 

The application itself is painless, bloodless and rapid, which makes it suitable for pediatric use in the clinic. However, it can be quite painful during the next 2-4 days especially on the weight bearing areas. People experience different degrees of pain and it can be due to different pain threshold or body reaction to the medication. 

The efficacy of the treatment can be increased by covering the wart with nonporous occlusion. Some use it for warts under the nails as it can spread under nails and into the nail fold. 

Advantages: Relatively low cost, success rate up to 80%, no pain during the application, low risk of scarring. 

Disadvantages: Multiple appointments in the clinic every 1-4 weeks, not recommended for patients with diabetes, neuropathy and poor circulation, unpredictable pain severity after each treatment, blister. 

FUN FACT: In its natural form, cantharidin is secreted by the male blister beetle and given to the female as a copulatory gift during mating. Afterwards, the female beetle covers her eggs with it as a defense against predators.

5- SWIFT Machine (microwave therapy)

Microwaves have been in clinical use for over 30 years and it has been proven that it cannot cause any damage to the DNA of living things. The microwaves that are emitted from SWIFT machine can generate heat in a limited and focused area on the skin. 

The applicator tip of the device that contacts the skin is single use to eliminate the risk of cross-contamination. There are some advantages of the microwave treatment over cryotherapy (freezing with liquid nitrogen). For example, the microwave travels in highly controlled and precise straight lines aligned with the device tip so there is minimal spread of heat or damage to the adjacent tissues. Both treatments are painful during the treatment but unlike cryotherapy there is usually no blistering or tenderness after SWIFT treatment. However, SWIFT treatment is more expensive. One advantage of this treatment compared to LASER is that SWIFT does not generate smoke or particulate debris which can potentially be risky for the practitioner or the patient. 

There is no pain after SWIFT treatment and patient can continue normal activity after each treatment. The patient needs 1 treatment per month for 3-5 months depending on the size and type of the lesions. During the treatment, we set the power of the microwave up to 10 Watt, which gives us about 3mm penetration of the heat. Each treatment normally consists of 3 application on each wart, each application lasts for only 2 seconds. We ask patients to stop using any topical on the warts at least 2 weeks prior to the treatment as it will significantly increase the pain during the treatment. 

For more information please visit the SWIFT company’s website by clicking HERE.

6- Needling (Falknor’s Technique):

The needling technique has been considered as somewhat a renaissance in chiropody/podiatry practice for wart treatment. It was first described by Dr. Falknor, an American practitioner in 1969 and then many podiatrists and dermatologists followed and modified his technique. This method involves multiple needle penetrations right into the wart under local anesthesia. 

The idea behind this treatment is to enhance immune response and also to introduce the virus into the deeper layers of skin, where the immune system can detect the viruses. In many cases, if we attack the main and first wart (the mother wart), then other warts, even on remote areas may be cleared. 

In one study, 69% success rate was reported, but there are other reports showing higher success rate. 

It is advised to avoid NSAIDs (Advil, Aspirin, Naproxen, etc.) for about 48 hours. These painkillers are anti-inflammatory and we do not want to reduce the inflammation after treatment as inflammatory response is the key to trigger immune response to wart infection. 

Advantages: Good success rate, can be done in one treatment session with 1 or 2 follow up appointments (1 week and 3 months later). After 3 months, if the wart still present, another needling treatment may be granted. Not much pain after the treatment. 

Disadvantages: Numbing the area is painful, risk of infection or bleeding if the technique is not properly done.

7- LASER (low or high level):

Different types of LASER can be used for treating warts. Currently our office is not equipped with hot LASER. 

Nd:YAG LASER has up to 96% cure rate. It basically burns the cells that contain the virus. This option is expensive. 

Low-Heat LASER: repeatedly raises the temperature of the area to a tolerated level of about 50 °C. 

CO2 LASER: Used on resistant warts. Can be painful after treatment, may leave scarring, may need multiple treatments, smoke from the burn can be hazardous if proper ventilation is not provided. 

 

8- Excision (surgery) = Curettage

This method is usually a last resort for stubborn warts. It is not suitable for warts that involve large areas of the skin. 

Advantages: Usually the fastest way to eliminate the wart with 65-94% success rate. Often only needs one treatment per site. 

Disadvantages: Freezing the area, especially at the bottom of the foot is painful. Also, there is still up to 33% chance of recurrence.  If the wart is at the bottom of the foot, surgery most likely ends up with scarring which can be permanently painful on weight bearing areas.  Other adverse effects (like any other surgery) includes post-operation pain, bleeding, infection, and potential recurrence. 

 

9- Cauterization

Similar to surgery or LASER, this method is to destruct the wart lesion. Can be painful during or after treatment, the smoke generated after burn can be hazardous for the practitioner or patient. For larger lesions it may need multiple appointments with or without numbing the area. Our office is not equipped with this treatment. 

 

10- Bleomycin

This is a chemotherapeutic agent that can be used for wart treatment. Not recommended for regular warts and is generally reserved for resistant warts that have failed multiple other treatments. This treatment is an intralesional injection of 0.1-1.0 cc of Bleomycin and may need local anesthesia as well. One study showed complete resolution of recalcitrant plantar warts in 87% of the patients with only 20% of the patients requiring a second injection. It can cause some damage to the healthy tissues around the wart, so precise injection is required. 

Advantages: No evidence of systemic toxicity, high success rate, only one or two injections, 

Disadvantages: Very painful during injection (so needs local anesthesia), risk of damage to the surrounding healthy tissues, may leave black eschar on the lesion that needs debridement 2-3 weeks after injection if it does not detach spontaneously, possible nail loss (temporary) or nail deformity (permanent) if injection done close to a nail. 

Note for practitioners: Typically, bleomycin sulphate (0.25-1 mg/ml) is injected up to 3 times to a maximum total dose of 4mg in up to 2 injection sessions with a maximum total dose of 2000 unit. Injection to the wart confirmed by observing blanching in the lesion. 

11- 5-Fu (5-Flurouracil = Efudex cream) 

This is another chemotherapeutic agent that can be used for wart treatment. It works by inhibiting cell growth of the infected skin cells. This treatment is also reserved for resistant warts. 

Patients need to apply 5% cream/solution of 5-FU on the lesion twice a day and cover with a tape for a month. One study showed that a combination of 5% 5-FU and 10% salicylic acid had 63% success rate compared with 23% when only salicylic acid used. 

It can also administer by intralesional injection of 40 mg/ml 5-FU weekly for up to 4 weeks (60% efficacy)  

Advantages: Relatively inexpensive, few office visits for paring (debriding) the warts, high success rate (some studies show up to 95%), generally painless

Disadvantages: Blistering, local irritation, and sometimes pain after each application. if used close to the nail, it can cause nail detachment (not recommended for warts under or around nails), can cause mild-moderate ulceration, contraindicated in pregnancy and breastfeeding. 

 

12- Aldera = imiquimod (5% cream)

This medication is a topical immunomodulation that is typically used for genital warts. However, skin warts such as plantar warts have also responded to imiquimod (Aldera) treatment. It stimulates cytokines (immune system). 

The treatment should be done after debriding the wart. One protocol involves applying the cream on the warts twice a day for up to 24 weeks. It can be combined with occlusion (duct tape) or salicylic acid. Another protocol suggests to apply the cream 3 times per week for plantar warts

Advantages: No pain, good success rate, well tolerated in compromised immune system, low recurrence rate, self-applied by adults, not many office visits required. 

Disadvantages: Expensive, long treatment plan, possible local skin reaction leading to inflammation or pain. 

13- Zinc and Vitamin A:

Zinc and vitamin A are known to have a mild effect on boosting immune system. There is no solid evidence that taking zinc and/or vitamin A alone clears the warts but there are no serious side effects to them, many practitioners suggest them as a complementary treatment. 

It has been suggested to taking 15mg zinc tablet and 10,000 Unit Vitamin A 2 times per day for 30 days can increase skin turnover and complement the main course of treatment. You can buy these supplements from any pharmacy without a prescription. 

If you would like to book an appointment please call us 519-942-4705 and if you have questions or want to send pictures of your warts please contact us at contact@orangevillefootclinic.com

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Some of the references: 

1- Plantar Warts: Epidemiology,Pathophysiology, and Clinical Management

2- The Treatment of Verrucae Pedis Using Falknor’s Needling Method: A Review of 46 Cases

3- What are the effects of heating the skin with microwaves?

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