Environment

As the skin is in constant contact with its surroundings, the environment is an important consideration when thinking about skin health. The immediate, local environment has a biological impact, thus if it is cold the skin responds with goose bumps, if it is hot it will sweat. A hot dry environment particularly one found in overheated homes can cause the skin to become very dry and itchy, particularly in the elderly. This section will look at the impact that environmental changes at a global level may have on the skin and touch on diseases related to poverty.

It is difficult to prove categorically that any long-term, global environmental changes have a direct impact on skin health. There are many confounding factors to consider, and it is therefore virtually impossible to make a direct link between degradation of the environment and changes in skin health. For example, there is no doubt that our earth has less ozone protection than it did, which means that we are less well protected from UV radiation than in previous centuries (Earth Observatory, 2009). How much the increase in skin cancers can be attributed to this and how much can be attributed to behaviour change (e.g. more exposure to UV radiation due to increased number of holidays in sunny climates) is difficult to say. However the Earth Observatory report quotes the United Nations Environment programme as saying that a sustained decrease of 1% in the ozone layer will ultimately lead to a 2–3% increase in skin cancer.

For atopic eczema, there would appear to be an upward trend over the last 30–40 years with an increasing prevalence of the disease (Williams, 1997). This trend seems to affect urban populations more than rural (Sherriff et al., 2002). This may be attributable to the hygiene hypothesis (see Box 1.1), but this theory is not agreed upon by all practitioners.

Box 1.1 Hygiene hypothesis This theory was first proposed in 1989 by a public health physician. He suggested that the rising levels of hay fever and other atopic conditions may be attributed to better living conditions. The fact that young children were exposed to fewer infections due to increased household cleanliness and decreased family size, meant they were more susceptible to developing atopic diseases including eczema. The theory behind this is an immunological one; by challenging a child’s immune system with infective processes it is less likely to ‘produce’ atopic symptoms (Strachan, 2000). This is explored further in section 9.

Diseases of poverty
Skin diseases of poverty are usually related to infective processes or infestations. Poor living environments, lack of access to clean water and hot climatic conditions all lead to increased likelihood of infections or infestations of the skin. Specific examples include scabies, which in resource poor countries, where people live in very close proximity to one another, affect significant proportions of the population, especially children. Fungal and bacterial infections are more likely when there is lack of clean washing water, when wounds cannot be properly dressed and when people may be immunocompromised through poor diet or HIV infection. Vector borne diseases for example those carried by a mosquito, are more common in tropical areas where disease carrying mosquitoes thrive. An example of such a disease is lymphatic filariasis (described in Box 1.2) which can cause lymphoedema, hydrocoele and significant skin changes. It is important because of the scale of the problem (1.3 billion people around the world are at risk of contracting the disease and 120 million are infected) and because of the serious impact that it has on quality of life and economic stability (Global Alliance for the Elimination of Lymphatic Filariasis, 2004).

Box 1.2 Lymphatic filariasis Lymphatic filariasis is a mosquito borne disease in which parasites known as filarial worms damage the lymphatic system. Small microfilariae are transmitted from mosquitoes to humans when the insect takes a blood meal. The microscopic parasites grow into worms which can reach 10 cm in length. These live in ‘nests’ in the lymphatic system causing significant damage. As a result lymphatic function is affected causing swelling and compromised skin function which, over time, can lead to elephantiasis. As a result of these huge limbs and grotesque skin changes, many people experience significant morbidity and disability. Working can become difficult or impossible. Undertaking activities of daily living is a challenge. Many people are ostracised from their communities and feel socially unacceptable. The good news, however, is that the disease can be eliminated through distribution of anti-parasitic drugs. This alongside a programme of managing the morbidity caused by lymphoedema and skin changes is a global health programme. For more details see www.filariasis.org.