Hyperkeratosis on the feet has many diverse causes. Through a careful patient assessment the cause will often be elucidated. When working in dermatology in the early 1990’s I learned a technique called “wet wrapping” which was used to treat patients with eczema. A wet wrap is designed to soothe inflamed skin and prevent scratching of the skin.
Having seen the effectiveness of the technique, I could see a potential use for it in podiatry, as a means of delivering intense moisturisation to thickened plantar epidermis. In 2016, I published a paper discussing the technique illustrated with a case study. As I frequently receive requests for details on the technique, I have decided to cover it in this blog.
What is wet wrapping used for?
The technique can be used for any patient where intense moisturisation is required, often to soften and reduce thick hyperkeratosis on the plantar surface of the foot. It offers a more gentle approach than scalpel debridement and can be carried out by the patient at home.
Prerequisites
The patient should be able to reach their own feet (or have a helpful family member at home who can assist).
The patient should own at least two pairs of socks to do this!
What should you use as the emollient?
Although you can use any emollient, for most patients, a urea containing product is the most appropriate choice owing to its physiological and clinical properties (outlined below). It's important to select an appropriate percentage of urea content.
Typically, 10% can be used effectively on most patients with no issues. Previous research has shown little difference in hydration in preparations containing between 5 and 20% urea [1].
How long should a course of treatment be?
Typically, as skin turnover works on a 28-35 day cycle, it requires 3 or 4 cycles for the urea to take effect. Generally at low concentrations, urea is well tolerated when used over long periods and effective at reducing dryness [2].
What are the advantages of wet wrapping with socks?
Alternative methods of occlusion include clingfilm or polythene bags placed over the feet. Wet wrapping using socks is advantageous as patients can easily wash their socks after use and re-use them as required. Moreover, socks when worn in bed don't rustle when you move in bed at night. Finally, if the patient has to get up in the middle of the night, socks are less slippery than walking on polyethylene bags or clingfilm.
THE TECHNIQUE
After a bath or shower, in the evening, the patient applies a generous amount of the urea based product to the heels and across the plantar surface of both feet. Ideally the feet should be warm and slightly damp for best effect.
A clean, DAMP sock is then applied to both feet over the emollient.
3. A clean, DRY sock was then applied over the top of the DAMP sock.
The patient then leaves this on overnight before removing the socks in the morning.
The feet can be washed in the morning and the socks put in the washing.
Frequency
The frequency is ultimately decided by the podiatrist, but in my experience, 3 nights a week is sufficient for most patients. I normally suggest every other night and then have the weekends free. This is easy to remember for patients.
At the conclusion of treatment, once a successful result has been achieved, the patient may reduce the frequency of wet wraps and return to daily urea-based emollient application.
Precautions
The technique is generally safe for most patients but of course, always check if the patient has any known allergies or sensitivities to any ingredient in the selected emollient.
At higher percentages, the chemistry of urea changes from keratoplastic (softener) to keratolytic (like salicylic acid) and should be used with caution, particularly on patients with neurovascular deficit / poor tissue viability.
Always advise the patient of a potential risk of slipping when wearing the socks.
The treatment should be discontinued if there is any skin reaction to the treatment.
Why use urea?
Although urea is considered to be a waste product it also occurs naturally within the epidermis as part of normal skin physiology. Keratinocytes in the lower epidermal layers express specific urea transporters and other channels known as aquaporins. Importing urea into the keratinocytes creates a humectant effect hydrating the cell and drawing in water through channels in the cell wall from the underlying dermis, maintaining cell turgidity and shape. Latterly, urea is also produced in the stratum corneum. A change from the neutral pH in the lower layers to a drier, acidic environment in the stratum corneum, promotes filaggrin breakdown into amino-acids and arginine. The latter being subsequently converted to ornithine, from which further urea is produced.
The effects of urea on human skin
Urea has been used topically for many years [3]. It properties as a hydrating agent have been established [4] but other effects have been less well researched. Grether-Beck and colleagues [5] investigated the properties of urea undertaking a range of experiments which highlighted some additional and previously unreported effects. In a urea versus placebo cream trial on normal skin they demonstrated that application of a urea-based cream, within hours, reduced trans-epidermal water loss, thus improving the skin barrier function. The effect was probably due to increased levels of filaggrin, involucrin and loricrin, particularly evident when a 20% urea formulation was used. In addition, they demonstrated how urea application stimulated expression of two antimicrobial peptides - cathelicidin (LL-37) and Beta-defensin 2.
The final part of their analysis also discovered that urea application upregulated the production of natural skin lipids – following urea application they were able to measure increases in the enzymes responsible for lipid synthesis after just 48 hours of exposure to the chemical increasing waterproofing in the outer layers of the epidermis.
The hydrating effects of urea have been observed – as a humectant it is able to attract and hold water within the epidermis giving it excellent emollient properties. Urea, as a small molecule also has the ability to cause conformational change in skin protein structures, effectively unfolding them making them more vulnerable to degradation and exfoliation – clinically this is seen as an epidermal thinning effect [6] without affecting normal skin physiology and integrity. This particular function being evident in lower strength formulations (less than 20%).
Conclusion
Wet wrapping is a simple and cost effective method of reducing hyperkeratosis on the feet. It can be easily carried out at home and requires little more than socks and a urea based emollient. The science of urea has been investigated and clearly shows how important it is to skin recovery by improving hydration and stimulating the skins natural mechanisms to restore normal homeostasis.
References
1. Cobos-Moreno, P., et al., Influence of creams with different urea concentrations on plantar skin hydration. J Tissue Viability, 2021. 30(4): p. 608-611.
2. Lacarrubba, F., et al., Clinical evidences of urea at low concentration. International Journal of Clinical Practice, 2020. 74(S187).
3. Kuzmina, N., L. Hagströmer, and L. Emtestam, Urea and sodium chloride in moisturisers for skin of the elderly--a comparative, double-blind, randomised study. Skin Pharmacol Appl Skin Physiol, 2002. 15(3): p. 166-74.
4. Cork, M.J. and S. Danby, Skin barrier breakdown: a renaissance in emollient therapy. British Journal of Nursing, 2009. 18(14): p. 872, 874, 876-7.
5. Grether-Beck, S., et al., Urea uptake enhances barrier function and antimicrobial defense in humans by regulating epidermal gene expression. J Invest Dermatol, 2012. 132(6): p. 1561-72.
6. Fluhr, J.W., C. Cavallotti, and E. Berardesca, Emollients, moisturizers, and keratolytic agents in psoriasis. Clinics in Dermatology, 2008. 26(4): p. 380-386.