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.
FREE Download full paper
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.
FREE Download full paper
