Too clean for comfort? Allergies and the environment

mnc-blog-pic-20161128Allergies seem to be increasing at a fast rate within our community and throughout the world. For instance, allergic rhinitis (including hay fever) affects 10-30 per cent of the population worldwide. One marker of allergic sensitisation, the presence of a specific immunoglobulin, IgE, is now found in up to 40 per cent of the population.

Allergies are the result of an abnormal immunological hypersensitivity to a wide variety of foods, drugs, environmental agents and insect allergies (including house dust). They may affect any age group, from infants to old age, and may vary in severity from being just a nuisance to fatal anaphylactic reactions.

It is therefore unwise to think of allergies and their causes as being similar in cause and mechanism of production.

An article in this paper (June 10, 2010) reported the response of the then Health Minister Joseph Cassar to a parliamentary question, saying that the prevalence of asthma had increased by 23 per cent over a period of six years. Moreover, there was a significant difference between different localities in Malta, with the highest prevalence being in the South Harbour region (11.7 per cent) compared to that in the southeast (8.5 per cent).

The role of pollution in causing allergic disorders has featured strongly in these discussions. Diesel exhaust particles (DEP) are well known to act as adjuvants, enhancing the immune response to antigenic stimulants like pollen. They have been shown to increase the production of IgE. It has been stated that the increased frequency of supersized tourist liners, which in the Mediterranean apparently use a more toxic form of fuel (compared to liners in the North Sea for instance), are likely to increase this problem.

Over cleanliness may not be ideal. In our efforts to protect our children from unseen pathogenic micro-organisms we are taking measures to ensure that our homes are not merely clean but practically sterile

While DEPs might explain the increased incidence of asthma, particularly in the more exposed geographic areas, they can hardly explain the explosion in the prevalence of food allergies.

At a recent meeting of the International Congress of Immunology in Melbourne (described by one participant as ‘the food allergy capital of the world’), various speakers tackled the problem of food allergies particularly in infants. Against all previous medical advice, experts now advocate the introduction of potentially allergic food like peanuts and egg products at about six months, when babies start being given solid foods (but not before four months of age).

One interesting theory advanced to explain this epidemic of allergic disorders, by Prof. Hamida Hammad from Belgium, relates to natural environmental conditions which seem to protect against the development of hyper-allergic disorders.

She found that children exposed to dust on dairy farms before the age of two are less likely to develop allergic disorders. Such children produce a protein called A20, which seems to be protective. This has led in Europe to building day-care centres on farms to stimulate the production of this protective material.

It has been known for some time that children who grow up in households with other siblings and pets, like dogs, are less likely to develop allergies. It is to be emphasised that the timing of such exposure seems to be critical. This has led to the conclusion that an obsession with cleanliness might not be a desirable thing, and a certain degree of exposure to the natural non-sterile environment might be a good thing.

On a historical note, the polio epidemic which struck in the aftermath of World War II seemed to attack children from better-off families rather than those from poorer ones (and by assumption, those less worried or over concerned with cleanliness), which fits in with the theory that over-cleanliness may not be ideal.

In our efforts to protect our children from unseen pathogenic micro-organisms we are taking extraordinary measures to ensure that our homes are not merely clean but practically sterile. Advertising products that “kill 99.9 per cent of household germs” encourage the thinking that all bacteria are dangerous, in defiance of the well-known fact that we live within a cloud of predominantly protective bacteria, without which life as we know it would be impossible.

This is not to say that basic hygiene is not fundamental to our health. It is still essential to prevent faecal contamination for instance. But even good advice, taken to excess, can actually be harmful.

[First published in Times of Malta on 27 November 2016]

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