Indoor allergen exposure is a risk factor for sensitization during the first three years of life

Methods and effectiveness of environmental control

In recent years the role of allergen exposure and atopy, and the interaction between them in the clinical expression of allergic disease, has been examined in a quantitative manner in epidemiologic studies. Such analyses suggest that avoidance of exposure to domestic allergens is a critical element in integrated strategies for both the prevention and the management of asthma. The promise of primary intervention in high-risk infants, as shown in the Isle of White study, has been confirmed in a recent study in Japan, and at least 4 similar trials are in progress. Applying these principles to the management of symptoms in patients with chronic asthma has proved more difficult, and it is likely that many earlier studies were poorly designed to test the hypothesis that allergen avoidance was clinically useful. Recent studies with patients moved to high altitudes during seasonal reductions in mite exposure and randomized controlled interventions in houses have all shown improvements in clinical manifestations of asthma. These recent trials have also demonstrated something that was less certain-that massive reductions in domestic allergen exposure can be achieved and that people will adopt the significant changes to their domestic environment and lifestyles if the risks and benefits are known. In the future, it seems likely that better study designs, as well as improvements in methods to monitor exposure and clinical outcomes, will provide further support for the role of allergen avoidance in the prevention and management of asthma.

Reversing the trend: reducing the prevalence of asthma

BACKGROUND

We urgently need to take steps towards reducing the prevalence of asthma in countries where the prevalence has become unacceptably high in recent years. Because we do not have any good information about causes of the increased prevalence, we cannot act directly to reverse the trend. Therefore we need to take an indirect approach and use known information of etiologic factors to try to reduce asthma in the next generation, while acknowledging that we may be dealing with different factors from those responsible for the increased prevalence. Any successful strategies will also help to ensure that developing countries do not attain such high rates of asthma in their children in coming years.

OBJECTIVE

This article summarizes the roles of the risk factors that identify "high-risk" children, that provide insights into mechanisms, or that have potential for primary prevention. The factors with the most potential for primary prevention are allergen exposure, parental smoking, breast-feeding, and dietary fatty acids.

CONCLUSION

In other health models, information about risk factors has been used in successful public health interventions. It is disappointing that the important risk factors for asthma are well documented but that there have been few trials of primary prevention and no changes in public health policies.

Is allergy prevention realistic and beneficial?

Allergic diseases among children have shown a marked increase during the last two or three decades, despite increased awareness of possible preventive measures. Preventive efforts have focused on new-borns and infants with a biparental history of allergy as they are at particularly high risk of developing allergic disease (40-60%). No good intervention studies have been performed in the general population, only in high-risk families. Unfortunately, so far known risk factors can only explain a small part of the recent increase in allergic diseases. The most important recommendation for everyone is not to smoke during pregnancy and when living/working with young children. Breast milk is the best for every baby, even from an immunologic aspect. Humidity problems should be reduced in homes, day-care centres and schools. It is probably wise not to keep furred pets indoors in homes when babies have a family history of allergy. However, the effect of such advice should be assessed, including the acceptability, compliance, costs and effectiveness. There is no doubt that we should go on with preventive measures both in babies at high risk of allergy and also in the general population. At the same time, research should try to find even more efficient ways to reduce the current "allergy epidemic".

Epidemiological analyses of the relationship between environmental pollution and asthma

Epidemiological studies performed on children and young adults indicate that the prevalence of asthma has increased over the past decades in a number of countries. Since genetic determinants alone are unlikely to explain these findings, environmental factors are expected to have an important impact on the prevalence of this disease. Environmental pollution, among many other factors, may play a role in the initiation and manifestation of asthma. However, there is little epidemiological evidence for a causal association between the classical major outdoor air pollutants, such as SO2 or particulate matter, and asthma. Evidence for an association between air pollution from motor vehicles and asthma is still controversial. Thus the indoor environment and other environmental determinants--including lifestyle factors--are likely to be more important as causes of asthma. Epidemiological studies are able to evaluate the effects of environmental factors on the health of human populations in their usual environments. In addition, they can measure associations between long-term environmental exposures and health outcomes. By using refined techniques for exposure and disease assessment, as well as time and cost-effective study designs, environmental epidemiology will increase the knowledge about the role of pollution as a possible cause of asthma.

House dust mite allergen exposure in infancy

BACKGROUND

Infancy may be a critical time for exposure to house dust mite allergens, when exposure to high levels can increase the risk of allergic sensitization and the development of asthma in later life.

OBJECTIVE

To measure house dust mite allergen (Der p 1) concentration in the infants' environment and examine lifestyle factors which may influence mite allergen exposure.

METHODS

Infants aged between 4 and 12 months (n = 134) from the western region of Sydney, Australia. participated. Reservoir dust samples were collected from four sites within each home: infant's bed, second bed (adult or second child's bed), lounge floor and sheepskins (where available). Settling aeroallergen was collected for 10-14 d in Petri dishes in the infant's room. Der p 1 was measured by ELISA. A questionnaire on types of bedding, sleeping and playing patterns of the infant was completed by the parents at the time of dust collection.

RESULTS

All infants were exposed to at least one site with Der p 1 concentrations greater than 10 microg/g fine dust. The mean settling aeroallergen level in the infants' room was 24 ng De p l/m2 day and this was weakly related to bed allergen levels (r=0.21, P<0.05). Mattress type had a weak effect on Der p 1 levels as measured in the whole bed (P = 0.07), while bed cover and bed type had no effect (P>0.6). The mean product of time spent at a site and its allergen concentration was highest for beds in 69% of infants.

CONCLUSION

The high level of allergen exposure in the environment of this group of infants places them at an increased risk of early sensitization and development of asthma. Any strategy to reduce asthma prevalence should address these high and avoidable levels.

Environmental allergens and childhood asthma

Exposure to allergens has been shown to lead to sensitization and to the subsequent development of airway hyperresponsiveness in genetically predisposed individuals. Increasing interest is being devoted to mechanisms for the prevention of allergen sensitization and asthma development. Primary prevention (avoiding the sensitization to allergens) requires a large effort as the majority of atopic sensitizations occur in children with no demonstrable risk at the birth. Secondary prevention (deterrence of disease expression despite prior IgE sensitization) requires methods for detecting the population at risk by means of large population screening. Tertiary prevention (minimizing the morbidity for those who already have the disease) may be achieved by allergen avoidance, which has been demonstrated to effectively decrease inflammation in symptomatic patients.

[What is new in pediatric pneumology?]

Have been selected for this review: 1) the recent and impressive development of high-resolution and spiral CT scan in pediatric thoracic imaging; 2) the emerging of new and promising therapies for asthma (long acting inhaled beta 2-agonists, leukotriene antagonists, anti-IgE monoclonal antibodies); 3) the multifactorial origin of asthma in childhood; 4) the development of thoracoscopic surgery, a minimal-invasive approach beneficial in numerous circumstances.

The allergy march: from food to pollen

There is epidemiological evidence, especially from longitudinal studies, that clinical manifestations of atopy as well as IgE antibodies against food and aeroallergens show a systematic sequence of events. The atopic march begins with food allergy associated gastrointestinal disorders and atopic dermatitis followed by respiratory allergies, i.e. asthma and atopic rhino-conjunctivitis. Detectable food antibodies, especially against egg and milk proteins, usually precede or accompany the early clinical symptoms and signs. Similarly, aeroallergen sensitization, first against indoor allergen antibodies, succeeded by outdoor allergen antibodies, precede the clinical manifestation of respiratory allergy. Early atopic events, either manifestation or sensitization can be used as risk markers or even predictors of atopic disorders to implement preventive measures. Early atopic dermatitis as well as elevated serum IgE antibodies against food allergens in the first two years of life in combination with a family history can be used as a predictor for aeroallergen sensitization.