Dry Skin
Emollients – key to maintaining foot health - Ivan Bristow PhD, Podiatrist
October 21, 2019
Dry skin is very common. Around 29% of working age adults have it, rising to nearly 90% of people aged 80 or over (1). It is one of the most common things that we see in clinic, but it often goes undiagnosed and untreated. It has many causes but what are the effects of dry skin and how can we best manage them?
The skin is the largest organ of the body and is also the main barrier between the internal environment and the outside world protecting against a range of threats such as bacteria, virus and fungi. Most of this protection comes from the outer most layer of the epidermis – the stratum corneum.
In healthy skin, the epidermis can be visualised as a brick wall with the skin cells being the bricks and the lipids produced by the skin being the mortar – holding the bricks together with an almost watertight seal. The bricks, are skin cells manufactured in the lowest level of the epidermis, the basal layer, which are modified as they ascend the layers to reach the outermost layer, the stratum corneum, in around 25 days or so. The mortar - skin lipids are produced from the breakdown of a molecule called filaggrin which degrades to a range of lipids (natural moisturising factors – NMF’s) which are expelled from the stratum granulosum onto the cells coating them in a waterproof layer which retains the skins moisture. The drier the skin becomes the less filaggrin is produced and so less lipid is released. Thus, creating a downward spiral of skin health. Consequently, small cracks appear in the skin and it becomes vulnerable to bacterial and fungal infections (2) along with irritants and potential allergens.
So, what are the main causes of dry skin? For most sufferers, the cause is physiological and not pathological i.e. the way we live rather than any given disease. Factors include:
- Over-bathing or showering
- “Hot” showers
- Use of shower gels, soaps and cleansers (often containing SLS and similar agents) which remove the skins natural lipids
- Soaking the skin
- Insufficient rinsing of soaps and gels
- Vigorous drying
- Humidity – central heating and air conditioning
- Sun exposure
Each time the skin is bathed, particularly if a shower gel or soap is used, removal of the skins NMF’s occurs, and a period is required for natural skin recovery to occur. Consequently, it’s a game of catch up for the skin leading to dryness. The skin recovery time increases with age probably explaining why dry skin is more prevalent in the older age groups. With showering comes another risk, particularly for the feet and legs. When soaps and gels are applied, gravity means they may run down the legs but rarely are the legs and feet properly rinsed after a shower, meaning the product remains on the skin provoking and prolonging further dryness in these areas.
In addition, there are a range of known medical disorders which can cause or exacerbate dry skin:
- Skin disorders – psoriasis, eczema, fungal infections etc.,
- Diabetes
- Peripheral vascular disease
- Anaemia
- Thyroid disorders
- Side effects of common drugs – statins
Statins are taken by many of our patients – their job is to lower cholesterol which they do very well. Unfortunately, cholesterol is a building block required in the manufacture of skin lipids so patients on these drugs are more likely to have dry skin problems (2).
Dry Skin and the Feet
Tinea pedis or dry skin?
Dry skin on the feet can be asymptomatic for the patient but is characterised by scale, redness, tightness, itching or occasionally dry fissuring. Tinea pedis is a great mimic of dry skin and so should be ruled out as a possible differential diagnosis. Two weeks daily application of a suitable antifungal such as clotrimazole (Canesten®) or terbinafine cream (Lamisil®) is a simple way to determine if a fungal infection is present on the skin. If the dry skin dramatically improves it suggests the cause was fungal in origin.
Treatment of dry skin
The mainstay of treatment is the regular application of an emollient to the feet. This is something which can be easily stocked and sold in the clinic. As a common condition, you can be assured that there will be a need for this by patients. So, which one do you stock? It is important to stress there is still no consensus on what the most effective emollients are (3). Which emollient is best for your patients is really down to patient choice (3, 4).
The skin on the foot has a very thick epidermis on the plantar area and for the most part is in a shoe for considerable periods of the day so additional factors need to be considered. Firstly, the foot being a cooler, distal area is generally best suited to heavier ointment-based preparations (usually labelled as “balms” or “heel balms”) which have a more occlusive effect than creams but potentially this can be a problem with socks and footwear. Patients may be best advised to apply lighter products such as a cream when they are more active keeping the more potent, heavier ointments for use in the evenings or overnight.
Figure 1 : A fingertip unit = 0.5 gram of product (5)
Urea preparations and other humectants
A humectant is a chemical which is able to draw and hold water – like a sponge. Emollient products with an added humectant have a stronger moisturising effect on the skin. Typical humectants include urea and lactic acid. Many of the preparations aimed specifically at the foot contain urea as the discerning ingredient with concentrations ranging from 5% to 40%. It is important to appreciate the chemistry of urea as its concentration dictates its chemical properties:
Percentage of Urea
Effect
1 - 20%
Emollient, humectant
20% – 30%
Mild to moderate keratolytic
40%
Moderate keratolytic
Proteolytic
Consequently, higher concentration containing preparations are best avoided in patients with poor tissue viability.
Research has also shown that regular urea application to the skin has additional properties (6) which make it particularly suitable for use on the feet. Firstly, with regular use it can thin epidermis without affecting the skin barrier function making it ideal for use on the plantar surface and on callused skin. In addition, it promotes the body’s natural production of filaggrin which in turn, increases the skins ability to produce more natural moisturising factors.
Key Points : Emollients
- There is no evidence-based consensus of what the best emollient is.
- Patient choice is key.
- Emollients are best applied after bathing or washing when the skin is damp for maximal effect.
- Pump applicators may be more economical for regular patient use than tubes of products.
- A fingertip unit (see Figure 1) of emollient in an adult is roughly 0.5 of a gram – around 4 g a day is required for a pair of dry feet.
- A single “shot” of a pump dispenses around 1 gram of emollient so two “shots” should be enough for one application to two feet.
- A urea containing product has added benefits for use on the foot.
- The percentage content of urea dictates the properties of the emollient.
References
1. Augustin M, Kirsten N, Körber A, Wilsmann-Theis D, Itschert G, Staubach-Renz P, et al. Prevalence, predictors and comorbidity of dry skin in the general population. J Eur Acad Dermatol Venereol. 2019:e-print ahead of publication.
2. Mekic S, Jacobs LC, Gunn DA, Mayes AE, Ikram MA, Pardo LM, et al. Prevalence and determinants for xerosis cutis in the middle-aged and elderly population: A cross-sectional study. J Am Acad Dermatol. 2019;81(4):963-9.e2.
3. British Dermatological Nursing Group. Best practice in emollient therapy. Dermatol Nurs. 2007;6(2):s1-s19.
4. Moncrieff G, Cork M, Lawton S, Kokiet S, Daly C, Clark C. Use of emollients in dry-skin conditions: consensus statement. Clin Exp Dermatol. 2013;38(3):231-8.
5. Finlay AY, Edwards PH, Harding KG. “Fingertip unit” in dermatology. Lancet. 1989;2(8655):155.
6. Bristow IR. Urea - the gold standard for emollients? Podiatry Now. 2016;19(10):20-3.
Further Reading
Bristow, I. R. (2012). “Emollients and the foot.” Podiatry Now: S1-S8.
Moncrieff, G., M. Cork, S. Lawton, S. Kokiet, C. Daly and C. Clark (2013). “Use of emollients in dry-skin conditions: consensus statement.” Clin Exp Dermatol 38(3): 231-238.