Risk levels for mite allergens. Are they meaningful?

Highly Permeable and Regenerative Microhoneycomb Filters

Allergic reactions can profoundly influence the quality of life. To address the health risks posed by allergens and overcome the permeability limitations of the current filter materials, this work introduces a novel microhoneycomb (MH) material for practical filter applications such as masks. Through a synthesis process integrating ice-templating and a gas-phase post-treatment with silane, MH achieves unprecedented levels of moisture resistance and mechanical stability while preserving the highly permeable microchannels. Notably, MH is extremely elastic, with a 92% recovery rate after being compressed to 80% deformation. The filtration efficiency surpasses 98.1% against pollutant particles that simulate airborne pollens, outperforming commercial counterparts with fifth-fold greater air permeability while ensuring unparalleled user comfort. Moreover, MH offers a sustainable solution, being easily regenerated through back-flow blowing, distinguishing it from conventional nonwoven fabrics. Finally, a prototype mask incorporating MH is presented, demonstrating its immense potential as a high-performance filtration material, effectively addressing health risks posed by allergens and other harmful particles.

To what extent is allergen exposure a risk factor for the development of allergic disease?

The role of allergen exposure in the development of allergic disease has been a matter of considerable debate, and our understanding of the importance of allergens has evolved over the last 25 years. Several observational and primary prevention studies have investigated these relationships, and different studies reported inconsistent, and sometimes opposite findings. It has to be emphasized that a clear understanding of how aeroallergen exposure occurs, and accurate and reproducible measurement of exposure are essential prerequisites for understanding the role of exposure. However, our current understanding of how we get exposed to allergens is not based on solid evidence, but on a number of assumptions, and we urgently need to develop better proxy measures (or indices) of exposure. In addition, the relative importance of the timing of exposure (e.g. early compared to exposure in later life) is unknown. It is also unclear which route of exposure is the most relevant (e.g. inhaled vs. oral vs. transcutaneous). Available data suggest that the dose-response relationship between allergen exposure and allergic disease may differ between different allergens, dose ranges and exposure patterns, and these relationships may further differ between different populations and geographical areas. It is increasingly clear that childhood asthma and atopy are not single phenotypes, and it is likely that allergen exposure has different effect on distinct subgroups under the umbrella terms of 'sensitization' and 'asthma'. Susceptibility to allergen exposure, other environmental exposures and their interactions may also differ between individuals with different genetic predispositions. However, the precise nature of these complex relationships is unclear. We need a holistic approach offered by systems biology, with integration of information on the standardized and reliable measures of exposures (including allergens and other relevant exposures) with genetic and biological data to fully understand the role of allergens in the development of allergic disease.

Respiratory allergy caused by house dust mites: What do we really know?

The house dust mite (HDM) is a major perennial allergen source and a significant cause of allergic rhinitis and allergic asthma. However, awareness of the condition remains generally low. This review assesses the links between exposure to HDM, development of the allergic response, and pathologic consequences in patients with respiratory allergic diseases. We investigate the epidemiology of HDM allergy to explore the interaction between mites and human subjects at the population, individual, and molecular levels. Core and recent publications were identified by using "house dust mite" as a key search term to evaluate the current knowledge of HDM epidemiology and pathophysiology. Prevalence data for HDM allergen sensitization vary from 65 to 130 million persons in the general population worldwide to as many as 50% among asthmatic patients. Heterogeneity of populations, terminology, and end points in the literature confound estimates, indicating the need for greater standardization in epidemiologic research. Exposure to allergens depends on multiple ecological strata, including climate and mite microhabitats within the domestic environment, with the latter providing opportunity for intervention measures to reduce allergen load. Inhaled mite aeroallergens are unusually virulent: they are able to activate both the adaptive and innate immune responses, potentially offering new avenues for intervention. The role of HDM allergens is crucial in the development of allergic rhinitis and asthma, but the translation of silent sensitization into symptomatic disease is still incompletely understood. Improved understanding of HDMs, their allergens, and their microhabitats will enable development of more effective outcomes for patients with HDM allergy.

Eastern Carolina Asthma Prevention Program (ECAPP): An Environmental Intervention Study Among Rural and Underserved Children with Asthma in Eastern North Carolina

OBJECTIVE

Asthma is the most common chronic childhood condition affecting 6.3 million (US) children aged less than 18 years. Home-based, multi-component, environmental intervention studies among children with asthma have demonstrated to be effective in reducing asthma symptoms. In this study, a local hospital and university developed an environmental intervention research pilot project, Eastern Carolina Asthma Prevention Program (ECAPP), to evaluate self-reported asthma symptoms, breathing measurements, and number of asthma-related emergency department (ED) visits among low-income, minority children with asthma living in rural, eastern North Carolina. Our goal was to develop a conceptual model and demonstrate any asthma respiratory improvements in children associated with our home-based, environmental intervention.

METHODS

This project used a single cohort, intervention design approach to compare self-reported asthma-related symptoms, breathing tests, and ED visits over a 6 month period between children with asthma in an intervention study group (n = 12) and children with asthma in a control study group (n = 7). The intervention study group received intense asthma education, three home visits, 2 week follow-up telephone calls, and environmental intervention products for reducing asthma triggers in the home. The control group received education at baseline and 2 week calls, but no intervention products.

RESULTS

At the end of the study period, significant improvements were observed in the intervention group compared with the control group. Overall, the intervention group experienced a 58% (46 ± SD 26.9) reduction in self-reported asthma symptoms; 76% (34 ± SD 29.7) decrease in rescue medicine; 12% (145 ± SD 11.3) increase in controller medicine; 37% decrease in mean exhaled nitric oxide levels and 33% fewer ED asthma-related visits.

CONCLUSION

As demonstrated, a combination of efforts appeared effective for improving asthma respiratory symptoms among children in the intervention group. ECAPP is a low cost pilot project that could readily be adapted and expanded into other communities throughout eastern North Carolina. Future efforts could include enhanced partnerships between environmental health professionals at local health departments and pediatric asthma programs at hospitals to carry out ECAPP.

Housing and child health

The connection between housing and health is well established. Physical, chemical, and biological aspects of the child's home, such as cleanliness, moisture, pests, noise, accessibility, injury risks, and other forms of housing environmental quality, all have the potential to influence multiple aspects of the health and development of children. Basic sanitation, reduced household crowding, other improvements in housing and expanded, and improved housing regulations have led to advances in children's health. For example, lead poisoning prevention policies have profoundly reduced childhood lead exposure in the United States. This and many other successes highlight the health benefits for families, particularly children, by targeting interventions that reduce or eliminate harmful exposures in the home. Additionally, parental mental health problems, food insecurity, domestic violence, and the presence of guns in children's homes all are largely experienced by children in their homes, which are not as yet considered part of the Healthy Homes agenda. There is a large movement and now a regulatory structure being put in place for healthy housing, which is becoming closely wedded with environmental health, public health, and the practice of pediatrics. The importance of homes in children's lives, history of healthy homes, asthma, and exposures to lead, carbon monoxide, secondhand/thirdhand smoke, radon, allergy triggers is discussed, as well as how changes in ambient temperature, increased humidity, poor ventilation, water quality, infectious diseases, housing structure, guns, electronic media, family structure, and domestic violence all affect children's health.

Pyroglyphid mites as a source of work-related allergens

Pyroglyphid mites are primarily associated with allergen exposure at home; hence the name house dust mites. However, we have found numerous studies reporting pyroglyhid mite levels in public and occupational settings. This review presents the findings of house dust mite allergens (family Pyroglyphidae, species Dermatophagoides) as potential work-related risk factors and proposes occupations at risk of house dust mite-related diseases. Pyroglyphid mites or their allergens are found in various workplaces, but clinically relevant exposures have been observed in hotels, cinemas, schools, day-care centres, libraries, public transportation (buses, trains, taxies, and airplanes), fishing-boats, submarines, poultry farms, and churches. Here we propose a classification of occupational risk as low (occasional exposure to mite allergen levels up to 2 μg g(-1)), moderate (exposure between 2 μg g(-1) and 10 μg g(-1)), and high (exposure >10 μg g(-1)). The classification of risk should include factors relevant for indoor mite population (climate, building characteristics, and cleaning schedule). To avoid development or aggravation of allergies associated with exposure to house dust mites at work, occupational physicians should assess exposure risk at work, propose proper protection, provide vocational guidance to persons at risk and conduct pre-employment and periodic examinations to diagnose new allergy cases. Protection at work should aim to control dust mite levels at work. Measures may include proper interior design and regular cleaning and building maintenance.

The Breathe-Easy Home: the impact of asthma-friendly home construction on clinical outcomes and trigger exposure

OBJECTIVES

We examined the asthma-control benefit of moving into an asthma-friendly Breathe-Easy home (BEH).

METHODS

We used a quasi-experimental design to compare the asthma outcomes of 2 groups of low-income children and adolescents with asthma: 34 participants who moved into a BEH, and a local matched cohort of 68 participants who had received a previous asthma-control intervention. Both groups received in-home asthma education. BEHs were constructed with moisture-reduction features, enhanced ventilation systems, and materials that minimized dust and off-gassing.

RESULTS

BEH residents' asthma-symptom-free days increased from a mean of 8.6 per 2 weeks in their old home to 12.4 after 1 year in the BEH. The proportion of BEH residents with an urgent asthma-related clinical visit in the previous 3 months decreased from 62% to 21%. BEH caretakers' quality of life increased significantly. The BEH group improved more than did the comparison group, but most differences in improvements were not significant. Exposures to mold, rodents, and moisture were reduced significantly in BEHs.

CONCLUSIONS

Children and adolescents with asthma who moved into an asthma-friendly home experienced large decreases in asthma morbidity and trigger exposure.

Diversity of allergen exposure: implications for the efficacy of environmental control

The prevalence of allergic diseases such as asthma, rhinitis, allergic conjunctivitis and atopic dermatitis has increased in the last decades. The relationship between allergen exposure, atopic sensitization and development of allergic diseases is widely described in the literature.

Aim

To evaluate measures for reducing allergen exposure as part of the treatment of allergic diseases.

Methods

An analysis was made of previous studies on allergen exposure done with a similar methodology in the central region of Brazil; the study included homes, hotels, cinemas, cars, taxis, buses and scholar transportation.

Results

High levels of Der p 1 and Der f 1 mite allergens were found in a large proportion of the sample in most of the environments included in those studies; there were higher levels of pet allergens in cars and school transportation vehicles.

Conclusion

The diversity of allergen exposure demonstrates the need for education about allergic diseases for patients and their families, as well as measures of reducing allergens in homes. This should be part of a global strategy of the management of allergic diseases, given that individuals live in society, not only in their houses.

Diversidade da exposição alergênica: implicações na obtenção da eficácia do controle ambiental

As doenças alérgicas, como a asma, rinite, conjuntivite alérgica e a dermatite atópica têm apresentado um aumento na sua prevalência nas últimas décadas. A relação entre exposição alergênica, sensibilização atópica e desenvolvimento de doenças alérgicas são amplamente descrita na literatura. OBJETIVO: Discutir a dificuldade no controle ambiental da exposição alergênica como parte do tratamento das doenças alérgicas. MÉTODOS: Analisar trabalhos de exposição alergênica realizados com metodologia similar na região central do Brasil, incluindo casas, hotéis, cinemas, carros, táxis, ônibus e transporte escolar. RESULTADOS: Níveis elevados dos alérgenos do grupo 1 de Dermatophagoides pteronyssinus (Der p 1) e de D. farinae (Der f 1), capazes de causar sensibilização e exacerbação de sintomas foram encontrados na maioria dos ambientes estudados em uma larga proporção das amostras, enquanto os alérgenos de animais domésticos atingiram maiores níveis em carros e veículos de transporte escolar. CONCLUSÃO: A diversidade da exposição alergênica mostra a necessidade de uma compreensão da doença alérgica pelos pacientes e familiares, e que as medidas de controle do ambiente doméstico fazem parte de uma estratégia global do tratamento das doenças alérgicas, uma vez que os indivíduos vivem em uma sociedade e não isoladas no interior de seus domicílios.

Dose-Response Relationships and Threshold Levels in Skin and Respiratory Allergy

A literature study was performed to evaluate dose-response relationships and no-effect levels for sensitization and elicitation in skin- and respiratory allergy. With respect to the skin, dose-response relationships and no-effect levels were found for both intradermal and topical induction, as well as for intradermal and topical elicitation of allergenic responses in epidemiological, clinical, and animal studies. Skin damage or irritation may result in a significant reduction of the no-effect level for a specific compound. With respect to the respiratory tract, dose-response relationships and no-effect levels for induction were found in several human as well as animal studies. Although dose-response relationships for elicitation were found in some epidemiological studies, concentration-response relationships were present only in a limited number of animal studies. Reported results suggest that especially relatively high peak concentrations can induce sensitization, and that prevention of such concentrations will prevent workers from developing respiratory allergy. Moreover, induction of skin sensitization may result in subsequent heightened respiratory responsiveness following inhalation exposure. The threshold concentration for the elicitation of allergic airway reactions in sensitized subjects is generally lower than the threshold to induce sensitization. Therefore, it is important to consider the low threshold levels for elicitation for recommendation of health-based occupational exposure limits, and to avoid high peak concentrations. Notwithstanding the observation of dose-response relationships and no-effect levels, due to a number of uncertainties, no definite conclusions can be drawn about absolute threshold values for allergens with respect to sensitization of and elicitation reactions in the skin and respiratory tract. Most predictive tests are generally meant to detect the potential of a chemical to induce skin and/or respiratory allergy at relatively high doses. Consequently, these tests do not provide information of dose-response relationships at lower doses such as found in, for example, occupational situations. In addition, the observed dose-response relationships and threshold values have been obtained by a wide variety of test methods using different techniques, such as intradermal exposure versus topical or inhalation exposure at the workplace, or using different endpoints, which all appear important for the outcome of the test. Therefore, especially with regard to respiratory allergy, standardized and validated dose-response test methods are urgently required in order to be able to recommend safe exposure levels for allergens at the workplace.

Mite and pet allergen exposure in hotels in Uberlândia, Midwestern Brazil

Mite allergens are involved in airway sensitization and allergic diseases. We evaluated the exposure to house dust-mite (Der p 1 and Der f 1) and pet (Fel d 1 and Can f 1) allergens in hotels in Uberlândia, Midwestern Brazil. A total of 140 dust samples were collected from bedding (n = 98) and carpet (n = 42) of bedrooms in 20 hotels enrolled for this study. Geometric mean (GM) levels of Der f 1 (11.30 microg/g of dust; 95% CI: 8.34-15.30 microg/g) were significantly higher than Der p 1 (0.15 microg/g of dust; 95% CI: 0.13-0.18 microg/g) in bedding dust samples (P < 0.001), regardless of the hotel classes. Der f 1 levels were significantly higher in bedding (11.30 microg/g of dust; 95% CI: 8.34-15.30 microg/g) than carpet (6.32 microg/g of dust; 95% CI: 4.31-9.26 microg/g) dust samples (P < 0.05). High levels of Der f 1 (>10 microg/g of dust) were found in 58%, 76%, and 69% of dust samples from Simple, Economical, and Tourist/Superior hotels, respectively, while GM levels of Fel d 1 (0.11 microg/g of dust; 95% CI: 0.09-0.14 microg/g) and Can f 1 (0.30 microg/g of dust; 95% CI: 0.20-0.44 microg/g) were relatively low. These results indicate that Der f 1 is the predominant allergen in hotels in Uberlândia, especially in bedding dust samples, regardless of the hotel classes and could represent an important risk factor for exacerbation of allergic symptoms in previously mite-sensitized guests.

PRACTICAL IMPLICATIONS

Mites and pets are important sources of indoor allergens. Most people spend the greatest part of their time indoors. Hotels can constitute an important allergen reservoir of the indoor environment and could represent an important risk for exacerbation of allergic symptoms in previously sensitized guests. Thus, hotels should also be included for planning indoor allergen avoidance as part of a global management strategy, especially in patients with respiratory allergy.

Current eczema in children is related to Der f 1 exposure but not to Der p 1 exposure

BACKGROUND

Mite allergen exposure is an important risk factor for specific IgE production and is associated with asthma, hay fever and eczema. Whether these associations are independent of mite species has not been investigated so far.

OBJECTIVES

To investigate the influence of exposure to the major house dust mite (HDM) allergens Der p 1 and Der f 1 on sensitization, respiratory symptoms, and especially on eczema and related skin symptoms in 6-7-year-old children.

METHODS

In a cross-sectional study in Augsburg (Bavaria, Germany) 1669 school beginners (mean age 6.5 years) were investigated in 1996. The concentrations of Der p 1 and Der f 1 were measured in dust samples from mattresses of 1081 children by enzyme-linked immunosorbent assay. The prevalence of atopy-related health outcomes was assessed by questionnaire, dermatological examination, skin prick testing and determination of specific serum IgE concentrations by radioallergosorbent test. Information about covariates was taken from questionnaires and interview data. Logistic regression was used to adjust for confounding.

RESULTS

The mean concentrations of Der p 1 and Der f 1 were 0.68 and 0.79 microg g(-1) dust, respectively. The relationship between the two species-specific allergens in individual homes was poor (Pearson correlation 0.2). Influencing variables were bedroom-sharing (Der p 1) and social status of the parents (Der f 1). Respiratory diseases were positively associated with both allergen concentrations [odds ratio (OR) between 1.1 and 2.6]. These associations were significant for sneezing attacks (Der p 1 and Der f 1). Reported prevalence of current (in the last 12 months) itchy skin rash was significantly associated with exposure to Der f 1 only (OR 2.4, P < 0.003); also a diagnosis of atopic eczema on the day of investigation was positively associated with Der f 1 only (OR 1.8, P = 0.14).

CONCLUSIONS

Studies on the effects of HDM exposure on eczema and allergies should consider specific effects of different mite species. This might have implications on assessment of allergen exposure and consecutive prevention or therapeutic measures.

The effect of encasings on quality of life in adult house dust mite allergic patients with rhinitis, asthma and/or atopic dermatitis

BACKGROUND

Environmental control has been put forward as an integral part of the management of house dust mite (HDM) allergy in sensitized patients. To validate this statement allergic disorders involved in HDM allergy--allergic asthma, rhinitis and atopic eczema/dermatitis syndrome (AEDS)--should be taken together and studied in terms of the efficacy of environmental control. Because a generic quality of life questionnaire exceeds the border of disease, this may be used as major outcome parameter.

RESEARCH OBJECTIVE

To study the effects of bedding encasings in HDM allergic patients with asthma, rhinitis and AEDS.

MATERIAL AND METHODS

A total of 224 adult HDM allergic patients with rhinitis and/or asthma and/or dermatitis were randomly allocated impermeable or nonimpermeable encasings for mattress, pillow and duvet. Short form 36 (SF-36) was filled in at baseline and after 12 months.

RESULTS

Lower physical (P = 0.01) and emotional (P < 0.001) sumscores were seen in females. Also, the presence of asthma resulted in lower physical sumscore (P = 0.01). However, no effect was seen of encasings on either sumscore.

CONCLUSION

Bedding encasings do not improve quality of life in a mixed population of subjects with combinations with rhinitis, asthma and atopic dermatitis and sensitized to HDMs.

Concentrations of cat and dust-mite allergens in dust samples from 92 large US office buildings from the BASE Study

The concentrations of cat (Fel d1) and dust-mite (Der f1 and Der p1) allergens were measured in 92 large office buildings in the US Environmental Protection Agency's Building Assessment Survey and Evaluation (BASE) Study (251 dust samples; one to four samples per building). Fel d1 was detected in almost all buildings and samples (91 buildings, 99%; 235 samples, 94%; range: <0.01-19 microg/g; median: 0.3 microg/g). Cat allergen exceeded 1 microg/g (a lower symptom threshold) in 56 samples (22%) from 45 buildings, but exceeded 8 microg/g (a sensitization threshold) in only two samples (1%) from two buildings. Der f1 or Der p1 was found in approximately half of all buildings and samples (63 and 70% of buildings; 45 and 51% of samples; range: <0.01-53 microg/g and <0.01-25 microg/g; median: <0.02 and 0.03 microg/g, respectively). Mite allergen exceeded 2 microg/g (a sensitization threshold) in seven samples (3%) from five buildings and exceeded 10 microg/g (a symptom threshold) in three samples (1%) from three buildings. Fel d1 concentration was significantly higher in samples collected in summer (June to September, 48 buildings), but cat allergen was not correlated with either mite allergen. Der f1, but not Der p1, concentration tended to be higher in samples collected in winter (December to April, 44 buildings), and the two mite allergens were significantly correlated only in winter. Cat and mite allergens were detected in 78% of representative US office buildings, but the concentrations seldom exceeded levels associated with sensitization or symptom provocation.

PRACTICAL IMPLICATIONS

The information on the concentrations of cat and dust-mite allergens in representative large US offices has expanded the baseline data available for interpretation of measurements from other building investigations. With suggested refinements, the BASE protocol for measurement of allergen concentrations in dust samples may serve as a guide to future studies of building characteristics, bioaerosol concentrations, and occupant perceptions of the indoor environment.

Four methods of sampling for dust mite allergen: differences in 'dust'

BACKGROUND

Measurement of exposure to the dust mite allergen Der p 1 is important in asthma research and is potentially useful in managing asthma. As no single measure can capture all characteristics of an exposure, it is important to recognize differences in the available methods of measuring exposure to Der p 1.

METHODS

Fourteen bedrooms and living rooms were sampled using four methods for 1 week. Airborne allergen was sampled by static Institute of Occupational Medicine samplers. Settling dust was collected on Petri dishes and an adhesive-membrane system (A-book). Vacuumed reservoir dust samples were collected from floors at the end of 1 week. Der p 1 was measured in all samples by enzyme-linked immunosorbent assay, except A-books, in which it was measured by Halogen immunoassay.

RESULTS

All four methods intercorrelated moderately (r range = 0.40-0.64, P = 0.04), except between allergen in reservoir dust (as microg/m2 and microg/g dust) and settling dust by Petri dishes (P = 0.2). Reservoir allergen, expressed as microg/m2, did not correlate with any measure, except reservoir allergen expressed as microg/g (r = 0.39, P = 0.04). No differences in these associations occurred between bedrooms and living rooms.

CONCLUSIONS

While the four methods examined correlated moderately, all have practical advantages and difficulties. No method can be considered as ideal for measuring individual exposure. For practicality, use of vacuum cleaner and Petri dish methods are recommended.

Environmental controls in the management of allergic asthma

Environmental allergen control is one of the four primary goals of good asthma management. The American Academy of Allergy, Asthma, and Immunology has published a position statement [78] that endorses the National Asthma Education and Prevention Program management guidelines [23] and recommends that every patient with persistent asthma be evaluated for environmental allergen sensitivity. Patients who have sensitivities should receive practical advice on allergen avoidance. An accumulating body of knowledge indicates that such measures, when strictly applied for a sufficient period of time, can indeed reduce asthma symptoms, need for medication, and airway hyperresponsiveness. Ongoing prospective trials in large numbers of patients are being conducted and should enhance the ability to make proper recommendations to patients.

B-cell isotype control in atopy and asthma assessed with cDNA array technology

B-cell isotype switching and the production of IgE is regulated by a variety of gene products through different mechanisms. A better understanding of these processes has the potential to identify markers of disease and new therapeutic targets. The aim of the study was to investigate human B-cell isotype control and IgE production in atopy and asthma with cDNA array technology. Eighteen atopic asthmatic, eight atopic nonasthmatic, and fourteen healthy control subjects were included. Peripheral blood mononuclear cells were separated by gradient centrifugation, mRNA was purified, and the reverse-transcribed probes were hybridized to cDNA membranes. Group differences were assessed with the Mann-Whitney U-test. Twenty-three of seventy-eight tested IgE-related genes had significantly altered expression in atopy and asthma compared with that in the healthy subjects. The differentially expressed genes include surface molecules involved in T- and B-cell interaction and activation, cytokines, intracellular signaling products, and transcription factors. In conclusion, both atopic nonasthmatic and atopic asthmatic individuals had activated proinflammatory pathways, a minimal requirement for B-cell isotype switching, and a clear net pro-IgE cytokine climate.