Is There A Rural/Urban Gradient In The Prevalence Of Eczema? A Systematic Review And What Can Be Done About It?

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One in 10 schoolchildren in the western world suffers from eczema and even developing nations have also seen an increasing trend in the last few decades. There are many proposals to explain the increased incidence, one area of relevance is the environmental impact. Falling under the often misused ‘hygeine hypothesis’ title it has been proposed that there is a reflective difference in the gradient between rural and urban children. Implying the environmental impact on the developing immune system of children is different and therefore less protective in the urban setting.

This concept has now been studied in a recent article in the British Journal of Dermatology.[1] By conducting a Medline and Embase data base review studies that compared the incidence between the two environments were reviewed. Some 26 papers were assessed with 19 demonstrating a higher risk for eczema in an urbanised area, of these 11 were regarded as being statistically significant. A further 6 studies showed a lower risk of eczema in an urbanised area, of which just 1 was statistically significant.

Comment

This paper concludes that there is some evidence of a higher risk for eczema in urban compared with rural areas, suggesting that place of residence may have a role in the pathogenesis of eczema.

What Can We Do About It

The earlier one starts to modify immunological responses to potential skin irritants the better the outcome – or at least this study suggests this. By asking mums at the end of pregnancy and during breast feeding a greater degree of immunological tolerance was passed on to their child reducing eczema in infants.[2] The probiotic milk contained Lactobacillus rhamnosus GG, Lactobacillus acidophilus La-5 and Bifidobacterium animalis subsp. lactis Bb-12

An earlier study also found that taking probiotics during pregnancy reduce incidence so eczema, suggesting that the foetus and neonate are able to collect information from the mum that reduces eczema risk.[3] In this double-blind, randomised, placebo-controlled trial, a mixture of probiotic bacteria selected by in-vitro experiments (Bifidobacterium bifidum, Bifidobacterium lactis, and Lactococcus lactis were used.

Comment

The role of individual bacterial strains are known to have differing effects on the recipient, in part this is due the ecology that exists in their own digestive tract at the time of ingestion as well as prior medication usage. Further maturation and re-balancing of the bacterial species may be compromised by food and by the immune activity levels at the time of ingestion. However, scientists are slowly piecing together bacterial mixes that may have a consistency above 50% in terms of outcome and this will exceed that achieved by medicines. Probiotics have many potential uses, selecting the right strain for the right immune response is what makes their use at times seem ineffective.

References


[1] Schram ME, Tedja AM, Spijker R, Bos JD, Williams HC, Spuls PI. Is there a rural/urban gradient in the prevalence of eczema? A systematic review. Br J Dermatol. 2010 May;162(5):964-73. Epub 2010 Mar 16.View Abstract

[2] Dotterud CK, Storrø O, Johnsen R, Oien T. Probiotics in pregnant women to prevent allergic disease: a randomised, double-blind trial. Br J Dermatol. 2010 Jun 9. View Abstract

[3] Niers L, Martín R, Rijkers G, Sengers F, Timmerman H, van Uden N, Smidt H, Kimpen J, Hoekstra M.The effects of selected probiotic strains on the development of eczema (the PandA study). Allergy. 2009 Sep;64(9):1349-58. Epub 2009 Apr 9. View Full Paper

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