The Pharmacist September/October 2018 - Page 41

CLINICAL KEY LEARNING POINTS • Cold weather can reduce the skin’s moisture content, making it more fragile • Patients should avoid bathing with soaps and hot – rather than warm – water, as this can further dry out the skin • The use of scarves to cover the face when outside in cold weather may help to prevent the exacerbation of rosacea Advising patients on winter skin problems The cold weather can often cause or exacerbate skin conditions. But pharmacists can play a key role in helping patients manage their symptoms, says Rod Tucker he reduction in temperature and humidity associated with the colder months affect the skin’s barrier function leading to a number of skin problems. The skin barrier prevents entry of allergens, irritants and micro-organisms and avoids excessive water loss. It is achieved by the uppermost layer of the epidermis, the stratum corneum (SC). The layer consists of between 10 and 30 stacked sheets of corneocytes embedded in a lipid-enriched lamellae. This structure is analogous to a brick wall, with the corneocyte ‘bricks’ surrounded by a lipid lamellae ‘mortar’. The stacked corneocyte sheets are connected via corneodesmosomes, analogous to the steel rods within reinforced T concrete, and provide tensile strength (ie resistance to shearing forces) to the skin. The SC cells are replaced every 28 days, with the rate of production of new cells, balanced by the desquamation (shedding) of old cells. To remain soft and flexible the skin requires between 10-15% of water, which derives from the lower levels of the epidermis and is maintained by the presence of water-binding molecules (humectants) – such as lactic acid, urea, glycerol and hyaluronic acid within the corneocytes – which are collectively referred to as ‘natural moisturising factor’ (NMF). The barrier is further enhanced by a hydrolipidic film on the skin surface, which comprises sweat, sebum and water. Cold air extracts moisture from the skin, leading to both reduced hydration and corneodesmosome degradation. The skin loses elasticity, becomes more fragile and there is an increase in the production of inflammatory mediators. Moreover, the dry air in centrally heated homes further reduces skin hydration. Common winter skin conditions Dry skin (xerosis) If the skin’s water content drops below 10%, the enzymes responsible for corneocyte desquamation no longer function properly. The corneocytes shrink reducing levels of NMF and the lipid lamellae appears broken (analogous to crumbling mortar in an old brick wall). These will create breaches in the skin’s barrier, allowing for greater water loss. Clinically, xerotic skin appears rough and September/October 2018 | The Pharmacist | 41