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Dry skin (xerosis) is a feature of conditions such as eczema, psoriasis and ichthyosis but it can also be associated with frequent washing, the use of harsh soaps and detergents, hard water and environmental factors such as temperature extremes and dry air conditioning. It can be mildly and temporarily troublesome or it can involve extensive dryness, fissuring of the skin and, if for example the hands are affected, impairment of function. It is, of course, also a cosmetic problem – it looks and feels unattractive.
The normal stratum corneum contains about 30 per cent water1 and this accounts for the skin’s pliability and smoothness. The common features of dry skin are mild scaling or flaking, roughness and a feeling of tightness; the first signs of xerosis appear as fine scaling and roughness when the moisture content of the stratum corneum falls below 10 per cent. Some dry skin also itches and, in the long-term, dry skin can become thickened and fissured.
The problems of dry skin are not only cosmetic. Dry, inflexible skin can make routine tasks difficult and dry, itchy skin is at risk of infection as a result of frequent scratching. In eczema and psoriasis, failure to treat the dryness effectively can lead to deterioration of these conditions. This is an area where self-care with support from a community pharmacist can play an important role. Most people with dry skin will treat themselves at some point and many will benefit from some help in choosing the most appropriate products and guidance in their effective use.
One aspect of the White Paper Our Health, Our Care, Our Say: A New Direction for Community Services2, published in January 2006, is the development of care closer to home. Dermatology is one of six specialities identified as being particularly suitable for this type of development. Community pharmacy input could make a valuable contribution here. Moreover, dermatological products account for a significant proportion of pharmaceutical sales – currently £75.1 million per annum on over-the-counter3 and £37.6 million per annum on prescription sales4, making a total of £112.7 million.
Healthy skin and dry skin
Normal, healthy skin is smooth and pliable. It is a remarkably effective barrier that prevents loss of water from skin and underlying tissues, and prevents ingress of bacteria, irritations and allergens. Two major factors contribute to the epidermal barrier – tightly-packed, well-hydrated corneocytes in the epidermis and multi-lamellar intercellular lipids. This can be envisaged as like a brick wall where the corneocytes are the bricks and the intercellular lipids are the mortar. In addition the epidermis contains water-retaining substances called natural moisturising factors (NMFs). These are complex mixtures of protein breakdown products. Reduction in these components leads to reduced barrier function, allowing loss of water from the skin, shrinkage of the corneocytes, disorganisation of the barrier and further water loss. Frequent washing and the use of soaps and detergents can remove some of the intercellular lipids. People with atopic eczema have a defect in the intercellular lipid production, which results in a less effective lipid barrier than normal. Once the barrier has been breached, further water loss occurs and dry skin is the result (Figure 1).
 Figure 1: Factors in the development of dry skin Ditchy skin is often a problem for elderly people. This is partly associated with the natural changes of ageing (decreased sebum and ceramide production) but it can be aggravated by environmental factors such as central heating and use of harsh washing products.
Emollients
Emollient products include creams, ointments, lotions, bath oils and soap substitutes. Although the terms “emollient” and “moisturiser” are often used interchangeably, in fact, emolliency refers to the ability of a product to fill the spaces between the desquamating corneocytes, whereas moisturising refers to the net decrease in transepidermal water loss after product application.
Emollients are believed to restore the integrity of the epidermal barrier in two ways. Firstly, they form an oily layer over the skin that prevents the evaporation of water. Consequently, the water trapped in the stratum corneum passes into the corneocytes, which swell, closing the gaps between cells. Secondly, emollients can penetrate deep into the stratum corneum and mimic the barrier effects of the deficient lipids. Effective use of emollients is particularly important in eczema as it can reduce the requirement for topical corticosteroids.
Choosing effectively
There is a bewildering array of emollients and it is sometimes suggested that the only real difference is price. However, this is not true – some are more effective than others and it is important to understand why. Probably the factor making the biggest difference is presence or absence of a humectant such as urea or glycerine. Humectants work by drawing water from the dermis into the epidermis (rather than by taking it from the atmosphere). Application of a 10 per cent urea cream can double the water-holding capacity of the stratum corneum5. Studies have shown that urea increases stratum corneum hydration and improves epidermal barrier function, when compared with vehicle alone6. Rehydration of stratum corneum is the key to success here. Urea is an NMF and is one of the most-widely studied humectants. Examples of emollients containing urea are Eucerin, Calmurid, Aquadrate and Nutraplus.
Another ingredient that gives some emollients special properties is polidocanol (lauromacrogols). This is added to a number of products for its mild anti-pruritic effect (e.g. Eucerin Dry Skin Relief Soothing Spray, Balneum Plus, E45 Itch Relief Cream).
Eczema is always itchy but many people with dry skin from other causes find that itching is a problem. Scratching often makes the itching worse and it damages the skin, leading to further drying. A good emollient with antipruritic effects can help to break this vicious cycle.
When selecting emollients it is important to remember that different products may be needed for different parts of the body. For example, a lighter product would be required for the face than for the limbs. Different products may also be needed for daytime and night-time use. Oil-in-water creams may be easier to use in the daytime but richer water-in-oil formulations can be beneficial at night. Emollient needs can also vary with season and activity. More, and sometimes richer, emollients are needed in winter to combat the effects of cold winds and central heating and on beach holidays to counteract the drying effects of sun, sand, sea and swimming pools.
To get the best out of emollients they must be applied frequently and generously – which could be three to four times a day or more. To do this most people will need to carry a small tube or tub in a handbag, briefcase or satchel for use during the day. Emollients should always be applied after bathing or showering – ideally within three minutes. It is also wise to apply emollients before exposure to a skin-drying situation, such as before going out in a cold wind or sunbathing.
Case study
Emma is a 32-year-old care assistant. She had eczema as a child but grew out of it as a teenager. She has recently moved to a hard water area and has developed troublesome dry skin on her forearms and shins. The skin on her hands has become rough and dry, and occasionally cracks and bleeds. She says that creams do not work for her. At first she used aqueous cream “because it rubs in easily and feels pleasant”, but it made little difference to the dryness and so she stopped using it. Her pharmacist advises her to use an emollient containing10 per cent urea after bathing and whenever her skin feels tight, and to use a soap-free wash product. When she returns to the pharmacy 10 days later she says she noticed a marked improvement within days and now realises that creams are not all the same.
References 1. Schwartz RA. Moisturizers (www.emedicine.com/derm/topic506.htm ).
2. Department of Health. Our Health, Our Care, Our Say: A New Direction for Community Services. January 2006 (www.dh.gov.uk ).
3. IRI All outlets, 52 w/e 22/04/06.
4. IMS 52 w/e 28/02/06.
5. Williams AC. Transdermal and topical drug delivery. London: Pharmaceutical Press, 2003.
6. Wohlrab W. Relevance of urea in external skin therapy. Hautartzt 1989; 40 (Suppl 1X): 35–41.
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