|
|||
 ForewordBy Professor Stephen Holgate |
|||
Allergic diseases of all types including rhinitis, asthma, atopic dermatitis, drug and food allergy and anaphylaxis are on the increase, but the underlying mechanisms responsible for this have yet to be found. Allergic disorders have strong genetic as well as environmental determinants. It is highly unlikely however that a change in genetic makeup could account for the trend, although it is of interest that the trend is highest amongst English speaking nations, suggesting that some genetic background is important. Of the many environmental determinants, it appears that allergen exposure per se is probably not as important as originally thought, although of course susceptible individuals must be exposed to a specific allergen in order to become sensitised. Since the trend is particularly manifest in children, it seems likely that any environmental factor(s) is manifesting early in life and even pre-natally. Although the nature of the environmental factors which are involved has eluded definition, recent evidence supports the idea that defects in the ability of children of atopic parents to protect themselves against allergen sensitization might be further enhanced in the absence of adequate programming by micro-organisms, or products from micro-organisms, present in the environment. This concept has been referred to as the ‘hygiene hypothesis’, but in many ways this is a misnomer, not least because the range of factors causing changes in microbial exposure that it considers are much wider than are commonly understood by the term ‘hygiene’. Indications are that bacterial, fungal and viral cell wall and nucleic acid products capable of stimulating Toll receptors as part of the innate immune response are fundamental in the early life origins of allergic disease, although the mechanisms involved are far from clear. However the idea that being too ‘clean’ is responsible for the immunological abnormalities that may be behind the changing trends in allergic disease is a gross oversimplification, and has led to misinterpretation of the concept. While much research effort is being focused on understanding the link between disordered immune responses and the trends in allergy, there has been little attempt to evaluate the validity or otherwise of the relationship to ‘hygiene’, and the adverse impact that uncritical acceptance of this hypothesis could have on public hygiene standards at a time when there is growing awareness of a need for improved rather than relaxed personal and community hygiene. This report looks at both aspects of the problem. The thoroughness of the review is refreshing, as is the commonsense approach to hygiene which is adopted. The report makes recommendations for adoption of a hygiene strategy based on risk assessment and stresses the importance of not relaxing hygiene standards, but ensuring that they are reinforced to protect the public from catastrophic infections, the consequences of which we are only too familiar. In the meantime, the study of cell and molecular biology combined with epidemiology and genetics should reveal how the immune response interacts with environmental factors and what aspects of the Westernised lifestyle are important in translating this into allergic disease. If the trend is to be reversed, research is needed to understand what factors direct an allergic response to a particular organ. Atopy, the genetic predisposition to develop allergy, may be present in up to 40% of a population but as yet a large number of these individuals remain asymptomatic. Professor Stephen Holgate University of Southampton School of Medicine Published by Nexthealth Srl, P.le Türr 5 – 20149 Milano - Italy |
|||
|
|||
Access the full report here or click on the links below to download individual sections
from the report. Section 1: Introduction |
|||
 |
|||
