Do Corn Plasters Work?

Do Corn plasters work - well yes and no, but the story also includes a bit about other treatments. Yes and no, as it depends on the cause. Poor application can lead to problems and patients are better off seeking advice from a podiatrist or qualified Foot Health Practitioner.

Today we know more about the humble corn than we have done in the past, but for many patients, sharp dissection on a cyclical basis is a quick fix, even if it is not permanent. Unlike a callus, however, your approach must be considered more cautiously.

Most patients would be happy to have the corn removed permanently. Others accept routine reduction keeps the foot comfortable. If a lesion is relatively new, the chances of responding are encouraging.

Scalpel treatment alone is disappointing. ConsultingFootPain (CFP) looks at some of the evidence behind concerns about chemical treatment and briefly looks at surgery.

The fat or hypodermis is shown together with the illustrative arrangement of collagen and elastin, which offers flexibility to the skin.

If the corn does not respond over several months, then there are diagnostic techniques, such as ultrasound, that can rule out problems within the hypodermis (fat) layer. Some podiatrists have reported complete resolution of corns, but there is no assurance from longer standing lesions, and infection may have occurred.

One reason corn plasters fail relates to viral infection with a wart or foreign body. This can complicate treatment in some cases as alternative treatment may be required.

The Corn Plaster

Salicylic acid (SA)

This product can come in several forms, from liquid to pastes. Available over the counter, each product comes with instructions. Salicylic acid (SA) is usually only used on the skin of feet and hands. The concentration of SA available to the public is usually under 20%, but even this can cause damage without careful preparation. Failure of the corn to be managed lies in the lack of correct preparation or incorrect product use. The chemical softens the corn and, in some cases, will allow the core to disappear. 

Most podiatrists do not recommend self-treatment as there are risks even if the public does find the SA medication helpful.

Farndon and co-workers conducted a controlled study in 2014 on 202 participants. The study was carefully carried out, and patients were followed up at three and twelve months. Pain resolved in many cases and showed better results than scalpel reduction alone. Their statement contains two important facts. The use of SA prolonged the corn’s reoccurrence, and secondly, SA (40%) was under podiatry supervision, which was why many in the study did so well.

Podophyllin

Akdemir used a mix of SA (30%), cantharidin (1%) and podophyllin (5%) as Canthacur-PS. As before, SA is often used in wart treatment on the surface of the skin of the feet and hands. Cantharidin is a toxic ingredient secreted from a beetle, and podophyllin comes from the roots of the mayapple plant. The product used by Akdemir was used as an alternative treatment for ‘callus’. Again, the research method included professional debridement with scalpels. The skin blistered, which had a risk of infection and was covered. Most patients  (79%) had one treatment – 72 patients. Some patients in the study received treatment for their hands, while 90% were treated for foot calluses or corns. An antibiotic dressing was used following treatment and covering the wound for 7 days. Follow-up was one year, and only one occurrence was recorded. This type of management would require professional supervision.

Bleomycin

Lee (2014) followed the same protocol used in Farndon’s research on SA but used an antibiotic, usually indicated for cancer management, for corn on the sole. The drug has antitumoral properties and is antibacterial and antiviral.

Fifty male patients selected from military forces had a total of 64 corns. One group was treated with bleomycin and debridement, and the others with debridement. In this case, bleomycin was injected with an anaesthetic. The treatment was 37% effective, but in some, the corn failed to clear, but the pain was reduced. When compared to mechanical debridement, only 10% improved. Partial improvement was recorded at 43%, so in real terms, 80% benefitted from this type of treatment. However, on average, 4.3 treatments were required, and over 60% needed paracetamol for post-injection discomfort. The follow-up period was around 3 months.

Silicone Injection

Tollafield (2001) studied thirty-one subjects with corns and applied 350-centistroke polydimethicone or saline over a 6- to 9-month period. The subjects were equally divided between male and female. The concept of silicone acts as a filler to compensate for the loss of the hypodermis (see diagram). The idea for feet originated from Sol Balkin.

Two randomly divided groups received silicone (16) and sterile saline (15). Essential histopathology was randomly undertaken on 11 subjects. While granulomatous reactions were only positively identified in one case, the author identified a problem with two other participants at 15 years. This study found no evidence to show that small quantities of medically prepared liquid silicone caused adverse reactions, although two cases were more sensitive after silicone injection. The ‘silicone experiment’ was published in 2021 by the author, 20 years after conducting the original work with Balkin (Tollafield, 2021). 

The use of chemicals has been well known and applied for several centuries and has included caustics such as silver nitrate. Older podiatry texts colourfully include remedies from times past (Le Rossignol, 1971). Many are unavailable today, and some are not considered effective.

Other over-the-counter remedies

Pharmacies sell corn pads as rings of felt to protect the area. These should be used for limited periods only as the skin can be easily damaged if these pads become wet or the skin is poor or sensitive.

Gel plasters do not contain SA but soften the corn by adding hydration to the skin. Currently, salicylic acid is the only viable treatment sold for use by the public.

Surgery

Surgery to the forefoot is the last stage of consideration but has a place for those corns, often known as intractable (plantar) keratoma, which causes pain and disability. Punch biopsy analysis (Güngör, 2014), full excision (Lopez & Kilmartin, 2016), plastic skin coverage (Saipoor & Maher, 2018), electrodesiccation (Bevans, 2010), and microwave (Case Reports Bristow, 2020) have been considered interventions. Some corns can affect tendons, and the author has published several articles on corns and calluses available on this site.

While microwave and freezing (cryotherapy) provide less invasive surgical techniques, their success and mode of action are still not wholly explained beyond replacing fat with a full-thickness skin flap.

Surgical excision with plastic flap created from adjacent skin. Podiatric Surgery case. (C) Tollafield DR. 2017

Hopefully, this article provides insight into why corns are difficult to manage and that, despite all our knowledge, a conclusive treatment still eludes us in the 21st century.

CFP considers that, in almost all cases, patients should consult a registered podiatrist or Foot Health Practitioner. (It is recommended to seek Foot Health Practitioners trained by The Institute of Podiatrists)

Mechanical means of removing a corn by superficial enucleation is fraught with disappointment unless the pressure can be relieved with insoles or orthoses.

References

• AKDEMIR, O., BILKAY, U., TIFTIKCIOGLU, Y.O., OZEK, C., YAN, H., ZHANG, F. and AKIN, Y. (2011), New alternative in treatment of callus. The Journal of Dermatology, 38: 146-150. https://doi-org.libaccess.hud.ac.uk/10.1111/j.1346-8138.2010.00978.x

• Bevans, J.S. & Bosson, G. 2010, “A comparison of electrosurgery and sharp debridement in the treatment of chronic neurovascular, neurofibrous and hard corns. A pragmatic randomised controlled trial”, vol. 20, no. 1, pp. 12-17.

• Bristow, I.R. & Webb, C.J. 2020, “Successful Treatment of Hard Corns in Two Patients Using Microwave Energy”, vol. 12, no. 3, pp. 213-218.

• Farage, Miranda et al. from Cutaneous and ocular toxicology. Structural Characteristics of the Aging Skin: A Review. DO – 10.1080/15569520701622951

• Farndon LJ, Vernon W, Walters SJ, Dixon S, Bradburn M, Concannon M, Potter J. The effectiveness of salicylic acid plasters compared with ‘usual’ scalpel debridement of corns: a randomised controlled trial. J Foot Ankle Res. 2013 Sep 24;6(1):40. doi: 10.1186/1757-1146-6-40. PMID: 24063387; PMCID: PMC3856524.

• Güngör, S., Bahçetepe, N. & Topal, I. 2014, “Removal of corns by punch incision: a retrospective analysis of 15 patients”, vol. 80, no. 1, pp. 41-43.

• Lee, W.J., Lee, S.M., Won, C.H., Chang, S.E., Lee, M.W., Choi, J.H. and Moon, K.C. (2014), Efficacy of intralesional bleomycin for the treatment of plantar hard corns. Int J Dermatol, 53: e572-e577. https://doi-org.libaccess.hud.ac.uk/10.1111/ijd.12586

• Lopez, FM Kilmartin TE Corn Cutting in the 21st Century. Podiatry Now. October. 2016

• Le Rossignol.J, N, Holliday, CB A Pharmacopoeia for Chiropodists. Faber & Faber Ltd. 1971

• Saipoor, A., Maher, A. & Hogg, L. 2018, “A retrospective audit of lesion excision and rotation skin flap for the treatment of intractable plantar keratosis”, vol. 34, pp. 23-27.

• Injectable Percutaneous Polydimethicone in the Treatment of Pedal Keratomas: A Single-Blind Randomized Trial. Tollafield DR, Holdcroft DJ, Singh R, Haque MS. Foot and Ankle Surgery. 2001. 40(5):295-301

• Tollafield, David R Foot Health Myths, Facts & Fables. Podiatry Reflections. Published by Busypencilcase Communications, 2020. The Silicone Experiment. pp.204-206 (Available from Amazon Books)

  
  

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