Indoor Aeroallergens Research Articles

The spectrum of aeroallergen sensitization in children diagnosed with asthma during first 2 years of life.

Aeroallergens may trigger symptoms in sensitized children with asthma. Documentation of sensitization is crucial to enable effective implementation of measures to prevent asthma exacerbations. To document the sensitization patterns of very young children (≤2 years) with asthma, we retrospectively analyzed the skin-prick test (SPT) results of the largest referral center in the country. During a 4-year period, 432 children (median age, 1.21 years; male/female, 2.35) were referred. All patients had recurrent wheezing attacks and good response to inhaled bronchodilators and were diagnosed with asthma by their referring physician. SPT with eight aeroallergens (grass mix, weed mix, tree mix, mold mix, house-dust mite, cockroach, cat, and dog) was performed in 209 patients (full panel group) and the remaining 223 were tested only with a mixture of two house-dust mites (Dermatophagoides pteronyssinus and Dermatophagoides farinae; house-dust mite group). The sensitization rates in house-dust mite and full panel groups were 3.2% (7/223) and 3.3% (7/209), respectively. Univariate and multivariate modeling was unable to identify a predictor for the presence of aeroallergen sensitization. During first 2 years of life, low rates of aeroallergen sensitization and lack of predictors of sensitization in children with asthma suggest that skin testing for aeroallergens may not be a routine procedure. When there is a high index of suspicion, testing only for indoor aeroallergens including house-dust mites, molds, and pets may identify the majority of sensitized children.

Pediatric allergy and immunology in Brazil

The subspecialty of pediatric allergy and immunology in Brazil is in its early years and progressing steadily. This review highlights the research developed in the past years aiming to show the characteristics of allergic and immunologic diseases in this vast country. Epidemiologic studies demonstrated the high prevalence of asthma in infants, children, and adolescents. Mortality rates and average annual variation of asthma hospitalization have reduced in all pediatric age groups. Indoor aeroallergen exposure is excessively high and contributes to the high rates of allergy sensitization. Prevalence of food allergy has increased to epidemic levels. Foods (35%), insect stings (30%), and drugs (23%) are the main etiological agents of anaphylaxis in children and adolescents. Molecular diagnosis of primary immunodeficiencies (PID) showed a high incidence of fungal infections including paracoccidioidomycosis in X-linked hyper-IgM syndrome, and the occurrence of BCG adverse reactions or other mycobacterial infections in patients with chronic granulomatous disease. Education in pediatric allergy and immunology is deficient for medical students, but residency programs are effective in training internists and pediatricians for the practice of allergy. The field of PID requires further training. Last, this review is a tribute to Prof. Dr. Charles Naspitz, one of the pioneers of our specialty in Brazil.

Environmental and occupational respiratory diseases – 1037. Sensitization to indoor aeroallergens in pediatric patients

A retrospective, observational and descriptive study reviewed the skin tests results for indoor aeroallergens in pediatric patients (≤ 16 years) in 2011. We evaluated the results of skin tests specifically for: Dermatophagoides farinae, Dermatophagoides pteronyssinus, Felis domesticus, Canis familiaris, Blattella germanica and Periplaneta americana. Results A total of 439 skin tests were performed for indoor aeroallergens in pediatric patients. There were 57.6% (n = 253) men and 42.4% (n = 186) women with mean age of 6.3 years. Patients were divided into the following age-groups: children under 3 years (17.8%, n = 78), 3 to 5 years (35%, n = 154), 6 to 12 years (36%, n = 158) and 13 to 16 years (11.2%, n = 49). The main diagnoses were chronic rhinopathy 88.9% (n = 390), asthma 16.7% (n = 73), atopic dermatitis 4.3% (n = 19) and other 7.3% (n = 32). At least 57.9% (n = 254) of the patients had one positive skin test for the evaluated allergens. In these patients, we found sensitization to D. farinae in 77.2% (n = 196), D. pteronyssinus 84.6% (n = 215), B. germanica 24% (n = 61), P. American 18.9% (n = 48), F. domesticus 18.5% (n = 47), and C. familiaris 10.2% (n = 26). Conclusions D. farinae, D. pteronyssinus and B. germanica were the most commonly aeroallergens found at the skin tests. When divided by age, F. domesticus and C. familiaris were more frequently found in children less than 3 year. In addition, D. farinae and D. pteronyssinus were identified more commonly in older age groups.

Occupational Lung Diseases among Soldiers Deployed to Iraq and Afghanistan

Military personnel deployed to Iraq and Afghanistan, from 2004 to the present, has served in a setting of unique environmental conditions. Among these are exposures to burning trash in open air "burn pits" lit on fire with jet fuel JP-8. Depending on trash burned--water bottles, styrofoam trays, medical waste, unexploded munitions, and computers--toxins may be released such as dioxins and n-hexane and benzene. Particulate matter air pollution culminates from these fires and fumes. Additional environmental exposures entail sandstorms (Haboob, Shamal, and Sharqi) which differ in direction and relationship to rain. These wars saw the first use of improvised explosive devices (roadside phosphate bombs),as well as vehicle improvised explosive devices (car bombs), which not only potentially aerosolize metals, but also create shock waves to induce lung injury via blast overpressure. Conventional mortar rounds are also used by Al Qaeda in both Iraq and Afghanistan. Outdoor aeroallergens from date palm trees are prevalent in southern Iraq by the Tigris and Euphrates rivers, while indoor aeroallergen aspergillus predominates during the rainy season. High altitude lung disease may also compound the problem, particularly in Kandahar, Afghanistan. Clinically, soldiers may present with new-onset asthma or fixed airway obstruction. Some have constrictive bronchiolitis and vascular remodeling on open lung biopsy - despite having normal spirometry and chest xrays and CT scans of the chest. Others have been found to have titanium and other metals in the lung (rare in nature). Still others have fulminant biopsy-proven sarcoidiosis. We found DNA probe-positive Mycobacterium Avium Complex in lung from a soldier who had pneumonia, while serving near stagnant water and camels and goats outside Abu Gharib. This review highlights potential exposures, clinical syndromes, and the Denver Working Group recommendations on post-deployment health.

Cockroach Allergen Bla g 7 Promotes TIM4 Expression in Dendritic Cells Leading to Th2 Polarization

As one of the most common sources of indoor aeroallergens worldwide, cockroach is important in causing rhinitis and asthma while the mechanisms underlying remain obscure. Since T helper (Th) type 2 polarization plays an important role in the pathogenesis of allergic diseases, we investigated the effect of Bla g 7, a pan-allergen from Blattella germanica (B. germanica), on Th polarization which is controlled by monocyte-derived dendritic cells (DCs). Challenged by recombinant Bla g 7 (rBla g 7), immature DCs obtained from human exhibited upregulated levels of TIM4, CD80, and CD86 and increased IL-13 secretion. Cocultured with CD4+ T cells, challenged DCs increased the ratio of IL-4+ versus IFN-γ+ of CD4+ T cells, suggesting a balance shift from Th1 to Th2. Moreover, antibodies against TIM4, CD80, and CD86 reversed the enhancement of IL-4+/IFN-γ+ ratio and alleviated the IL-13 release induced by rBla g 7, indicating that the Th2 polarization provoked by rBla g 7 challenged DCs is via TIM4-, CD80-, and CD86-dependent mechanisms. In conclusion, the present findings implied a crucial role of Bla g 7 in the development of cockroach allergy and highlighted an involvement of DCs-induced Th2 polarization in cockroach allergy.

Domestic exposure to aeroallergens in Hong Kong families with asthmatic children

Indoor aeroallergen exposures increased asthma symptoms in Caucasians, but their determinants and relationship to asthma and allergy in Asians are unclear. This study investigated exposures to cat, cockroach, and Blomia tropicalis allergens in 115 Hong Kong families with asthmatic children. Patients underwent exhaled nitric oxide and spirometric measurements. Home visits were made within 2 weeks during which parents completed a standardized questionnaire. Fel d 1, Bla g 2, and Blo t 5 in dust samples collected from patients' mattresses, bedroom floors, and living room floors were measured by immunoassays. These aeroallergens were only detectable in some homes (38-55% for Fel d 1; 9-21% for Bla g 2, and 7-14% for Blo t 5). The presence of cat and/or dog was a strong determinant for Fel d 1 in all indoor sites. The timing and frequency of bedding change was associated with Bla g 2 levels, whereas the timing of bedroom floor cleaning was a consistent factor for Blo t 5 levels. Asthmatic children in families with high allergen exposure were more likely to have ≥4 wheezing attacks in preceding 12 months and exercise-induced wheezing than those with normal allergen exposure (P = 0.051 and 0.030, respectively). Mattress levels of all three allergens were also associated with severity of several allergy symptoms (P = 0.025-0.005). None of these aeroallergens correlated with exhaled nitric oxide and spirometric parameters. This study identifies determinants for cat, cockroach, and B. tropicalis levels in Hong Kong families with asthmatic children. These exposures are associated with severity of allergy symptoms.

Age-Specific Prevalence of Outdoor and Indoor Aeroallergen Sensitization in Boston

Questions exist regarding the appropriate age for referral of an atopic child to an allergist for environmental skin prick testing. This study evaluates age-specific prevalence of sensitization to aeroallergens from infancy through adolescence. A total of 1394 patients were skin tested, with 57.2% being sensitized to at least 1 aeroallergen. In children younger than 2, the authors found that 26.5% were sensitized, including to dogs (15.5%) and cats (9.2%). Additionally, tree sensitization was demonstrated in the youngest age group (7.8% at 0-2 years; 17.1% at 2-4 years), including in 3 infants less than 1 year old. Sensitization rates to dust mites and trees were the highest in all ages above 4 years, with a peak tree sensitization of 56.4% at 10 to 12 years and a peak dust mite sensitization of 56.8% in the >12 group. Overall, the authors observed increasing sensitization rates throughout childhood for indoor and outdoor aeroallergens (P < .001). Aeroallergen sensitization begins at a young age and increases during childhood.

Resuspension of indoor aeroallergens and relationship to lung inflammation in asthmatic children

Studies have shown links between the concentration of allergens found in homes and asthma. Inhalation of allergens present in settled residential dust can occur when the dust is resuspended via human activity or air currents. Although previous studies have measured allergen concentrations in homes, the focus has been on the presence of the allergens in settled dust samples. However, the actual inhalation exposure is to airborne allergens. The relationship between the settled dust composition and suspended allergens and endotoxin and the effect of exposure of these aeroallergens to asthmatics are not well understood for species typically present indoors. In this study, settled dust and airborne particulate matter samples were collected in the homes and school classrooms of asthmatic children of ages 9 to 16 and analyzed for endotoxin and allergens including dust mite and cockroach allergen, and dog and cat dander (Der p1, Der f1, Bla g1, Can f1, and Fel d1, respectively). Concentrations of cockroach allergen were below detection limit for all samples. Measurements of the settled dust samples show higher dust mite allergen in bedroom samples than in living room samples. Concentrations of airborne endotoxin and indoor allergens were generally higher in the homes than those measured at school. Within the homes, higher concentrations of airborne allergens and endotoxin were observed in the living rooms compared to the bedrooms. Resuspension rates for endotoxin, dust mite allergen, and, cat and dog dander were estimated in this study. Calculated resuspension rates for cat dander (8.1×10−7±3.5×10−7min−1) and dust mite allergen (2.1×10−6±7.6×10−7min−1and 1.4×10−5±4.6×10−6min−1 for Der p 1 and Der f 1, respectively) were found to be higher than those for dog dander (3.1×10−7±1.3×10−7min−1) and endotoxin (3.6×10−7±1.6×10−7min−1). Markers of asthma inflammation including nitrate in exhaled breath condensate (EBC) and exhaled nitric oxide (eNO), were correlated with the concentrations of dust mite allergen (Der p 1) (Spearman r=0.598; p-value=0.068 for EBC and Spearman r=0.819; p-value=0.007 for eNO) and cat dander (Fel d 1) (Spearman r=0.917; p-value=0.0002 for EBC and Spearman r=0.697; p-value=0.054 for eNO) present in PM10 samples.

Post 9/11: High asthma rates among children in Chinatown, New York

We reported increased rates of childhood asthma and worsening of preexisting asthma in Chinatown near the World Trade Center (WTC) after September 11, 2001. This conclusion was corroborated by the WTC Health Registry in 2003, which showed asthma prevalence in children <5 years old was higher than national estimates. In 2002, ethnic Chinese in New York City (NYC), based on 2000 U.S. Census addresses, were reported to have the lowest levels of asthma compared with other ethnic NYC neighborhoods. This study was designed to determine if Chinatown asthma rates are still higher than other ethnic neighborhoods and if rates decreased since 2003. We surveyed 353 parents of children at a Chinatown elementary school, conducted spirometry on 202 students, measured air pollution (PM2.5), and sampled dust from the floor of the school during 2008 for concentrations of dust-mite antigens, cat, rat, mouse, and cockroach. Asthma rates of 14.4% were reported in children who refused spirometry if they lived <1 mi from the WTC. The rate was 4.9% if they lived farther away. Twenty-nine percent of all students (4-12 years old) who had spirometry showed a forced expiratory volume at 1 second (FEV(1)) of <80% predicted normal. Among children who were alive in 2001, 17.4% had an FEV(1) of < or = 75% predicted. The concentration of PM2.5 reached a high level of 40 microg/m(3). Indoor aeroallergen concentrations were negligible. Chinatown asthma rates are still higher than among other groups (29% versus the NYC reference rate of 13%). High air pollution levels may account for increased asthma incidence. It is possible that exposure to toxins on September 11, 2001 accentuated the effect of subsequent exposure to air pollution.

The non‐proteolytic house dust mite allergen Der p 2 induce NF‐κB and MAPK dependent activation of bronchial epithelial cells

House dust mites (HDM) are well-known as a source of indoor aeroallergens and for causing allergic airway diseases. Some proteolytic HDM allergens are known to activate respiratory epithelial cells to produce pro-inflammatory mediators, while there is limited knowledge regarding such activity among non-proteolytic HDM allergens. To investigate whether Der p 2, a major non-proteolytic allergen of Dermatophagoides pteronyssinus, activates respiratory epithelial cells to produce mediators involved in asthma pathogenesis and to elucidate the mechanism of such activation. The human bronchial epithelial cell line BEAS-2B, normal human bronchial epithelial (NHBE) cells and the alveolar epithelial cell line A549 were exposed to recombinant Der p 2. Following exposure, we analysed a panel of soluble mediators and cell adhesion receptors involved in asthma pathogenesis by promoting recruitment, survival and binding of inflammatory cells. The involvement of nuclear factor (NF)-kappaB and mitogen-activated protein kinases (MAPKs) was studied using specific inhibitors. Der p 2 activated bronchial BEAS-2B and NHBE cells, but not alveolar A549 cells. In BEAS-2B cells Der p 2 induced dose-dependent up-regulation in both mRNA level and protein secretion of granulocyte-macrophage colony-stimulating factor, IL-6, IL-8, monocyte-chemotactic protein-1 and macrophage inflammatory protein-3alpha. Secretion as well as surface expression of intercellular adhesion molecule (ICAM)-1 was also up-regulated, which was associated with increased adhesion of monocytes to the epithelial cells. The release of cytokines and chemokines was regulated by NF-kappaB and MAPK activation in different ways, while expression of ICAM-1 was solely dependent on NF-kappaB activation. These results show that Der p 2 activates respiratory epithelial cells, indicating that this non-proteolytic allergen, in addition to its immunogenic properties, can aggravate respiratory airway disease by adjuvant-like activation of the lung epithelium.

Asthma, allergy, the athlete and the Olympics

As the 2008 Summer Olympics in Beijing approach, both the general public and health care professionals are gaining interest in the potential health implications of sport. When asthma and allergy are present in athletes, this may affect their performance and achievements and justify the special attention of health care professionals who specialize in taking care of top athletes. However, the impact of allergy and asthma on sport and exercise goes further than just top athletes. The Editors of Allergy decided that in this issue they would focus the attention of allergy and asthma specialists by presenting a series of articles on the relationship between sport, asthma and allergy in the hope that an increased awareness of these problems would be highlighted not only for sports medicine doctors but also for all practicing allergists. Exercise-induced asthma (EIA) is a general concern for growing children and adolescents. In most international guidelines, one of the main objectives of treating asthma during childhood is for the child to be able to master EIA. Also among athletes, and especially elite athletes, EIA and bronchial hyperresponsiveness (BHR) have become major problems with regard to the correct diagnosis and to treatment. EIA is increasingly common among the top athletes of several different types of sport. Traditionally this has been reported mainly in athletes competing in endurance sports in cold climates, especially among crosscountry skiers (1, 2) and swimmers (3, 4), but also among endurance athletes in summer sports (5). A surprisingly high prevalence of asthma (56%) diagnosed by the reversibility of lung function to inhaled s2-agonists (56%) was reported among professional Canadian football players (6). The prevalence of EIA among top athletes has increased over the past decades. Weiler et al. reported 11% prevalence of EIA among American athletes participating in the 1984 Summer Olympic Games (7) and an increase to a prevalence of more than 20% was noticed among American participants in the 1996 Summer Olympic Games in Atlanta (8).

Reduction in indoor aeroallergen by using an xtreme 3000 air purifier

Reduction in indoor aeroallergen by using an xtreme 3000 air purifier

Allergens and allergic diseases in children.

The prevalence of allergic diseases is increasing gradually. Exposure to allergens is one of the trigger factors for symptoms in sensitized individuals. House dust mites and cockroach are the two most common indoor aeroallergens in Taiwan. There are wide differences in the numbers in different locations and in different seasons of these allergens. Sensitization to food allergens is prominent in young infants and can predict further aeroallergen sensitization. However, whether early exposure to allergens might develop or prevent allergic diseases in later childhood requires further research. Up to the present, allergen avoidance has demonstrated no prominent clinical efficacy in the improvement of allergic symptoms, although it is able to reduce allergen load in the environment. In a clinical regard, allergen avoidance should still be included as a part of treatment plans and be well explained to patients.

Childhood Asthma and Indoor Aeroallergens and Endotoxin in Palestine: A Case-Control Study

This study was carried out to evaluate the relationship between wheezing or sensitization and concentrations of mites, cat and dog allergens, and bacterial endotoxin in Palestine. A nested case-control involved analysis of mattress and floor dust from a 110 children's houses with reported wheezing and without wheezing. We found no consistent associations between allergen levels and either wheeze or specific atopic sensitization. Furthermore, no clear associations between mattress endotoxin levels and wheeze or atopy were found. Endotoxin in floor dust was inversely associated with atopic sensitization and wheeze, statistically significant only for atopic wheeze. Finally, a nonsignificant inverse association was observed between living room endotoxin and atopy within the non-wheezing control group. In conclusion, although our study found mostly negative results, it does suggest that endotoxin on living room floors might protect against atopic wheeze. However, this finding should be interpreted with caution due the relatively small sample size of the study and requires further confirmation.

Assessment of indoor allergen exposure

Of the four modes of treating human allergic disease, avoidance or separation of the allergic patient from the allergen source is most effective and least expensive. The clinical immunology laboratory has established efficient and inexpensive "reservoir" dust sampling and processing procedures to obtain a surface dust specimen that reflects the allergen burden of the environment. Following extraction, allergens are quantified by reproducible, validated immunoenzymetric assays for the quantification of "indicator" aeroallergen levels in home, school, and work environments. In this paper, the strategies and methods for collecting and processing dust samples are discussed, and assays are reviewed for quantifying indoor aeroallergen exposure from dust mites (Der p 1 and 2, Der f 1 and 2), animals (cat: Fel d 1; dog: Can f 1; mouse: Mus m 1; rat: Rat n 1), and insects (cockroach: Bla g 1 and 2). Accurate quantification of the levels of allergen in indoor environments facilitates avoidance therapy by identifying environmental risk factors for asthma and allergy exacerbation and allowing the allergic patient to monitor the effectiveness of environmental remediation actions.

Molecular cloning and characterization of full‐length cDNAs encoding a novel high‐molecular‐weight Dermatophagoides pteronyssinus mite allergen, Der p 11

Dermatophagoides pteronyssinus (Dp) and D. farinae (Df) mites are the most important source of indoor aeroallergens. Most Dp mite allergens identified to date have relatively low molecular weights (MWs). Identification of high-MW mite allergens is a crucial step in characterizing the complete spectrum of mite allergens and to provide appropriate tools for diagnostic and therapeutic application. The full-length Der p 11 cDNA clone was isolated using cDNA library immunoscreening, the 5'-3' rapid amplification of cDNA ends (RACE) system and polymerase chain reactions (PCR). The whole cDNA insert and its PCR-derived DNA fragments (p1 to p4) were generated and expressed in the Escherichia coli expression system. The allergenicity of the recombinant protein and its peptide fragments was examined by IgE immunodot assays. The IgE-binding reactivity of rDer p 11 was analyzed in the serum of 50 asthmatic children with positive reactivity to Dp mite extract. Its recombinant peptide fragments were also examined by immunodot assays in 30 mite-allergic children. Der p 11 cDNA consists of a 2625-bp open reading frame encoding a 103-kDa protein with 875 amino acids. It exhibits significant homology with the paramyosin of other invertebrates. The protein sequence alignment of this newly identified Dp mite allergen (denominated as Der p 11) revealed over 89% identity with Der f 11 and Blo t 1. Among 50 Dp-sensitive asthmatic children, rDer p 11 showed positive IgE-binding reactivity to 39 patients (78%). Using immunodot assays, multiple human IgE-binding activities were demonstrated in all four fragments of Der p 11. Using immunoblot assays, the dominant IgG-binding epitope for monoclonal antibody (mAb642) was located in fragment p3 only. In immunoblot assays, cross-inhibition between rDer p 11 and rDer f 11 was up to 73-80% at concentrations of 100 microg/ml. This study confirms that the newly identified recombinant Der p 11 is a novel and important high-MW Dp mite allergen for asthmatic children. Our data also indicates that human IgE-binding major epitopes are scattered over the entire molecule of Der p 11.

Aeroallergen sensitization in pediatric allergic rhinitis in Singapore: is air-conditioning a factor in the tropics?

Singapore is a unique blend of a tropical environment with a high standard of hygiene and public health care. The objective was to define the prevalence, clinical characteristics, and environmental risk factors of specific aeroallergen sensitization in pediatric allergic rhinitis patients in this unique environment. The method adopted was a retrospective analysis of allergic rhinitis patients, undergoing aeroallergen skin prick testing (SPT), in the outpatient specialty clinic of the KK Children's hospital, from July 2001 to June 2002. A total of 202 patients were included, 161 (80%) males, 167 (83%) Chinese, age mean 7.6 yr (range 2-14 yr). The most prevalent clinical symptoms were: watery rhinorrhea 61%, blocked nose 61%, sneezing 52%, snoring 17%, and epistaxis 12%. SPT results were positive for house dust mites in 97% of children, pets (20%), molds (19%), pollens (15%), and kapok (10%). Mold sensitization was significantly more prevalent in households without air-conditioning (aircon), 49% vs. 10% with aircon (odds ratio 9.4, 95% CI 3.8-22.9). Polysensitization (sensitization to three or more allergens) was similarly more prevalent in households without aircon, 51% vs. 14% with aircon (odds ratio 6.4, 95% CI 2.8-14.7). It was concluded that indoor aeroallergen sensitization is the major associated factor with clinical allergic rhinitis in children in Singapore. Patients living in households without air-conditioning are at increased risk of mold sensitization and polysensitization.

Comparison of monoclonal antibodies produced by in vitro and in vivo methods

Rationale The need for the production of large amounts of specific monoclonal antibodies (Mabs) to detect and quantify indoor aeroallergens depends on the induction of ascites mice. Stringent animal regulations have restricted investigators from relying on this method. Various innovative in vitro production methods have been developed with varying degrees of success. We have compared the production of Mabs by in vitro method, using Animal Component Free Medium in the CL-1000 flask with that of in vivo induced ascites in Balb/C mice. Methods Monoclonal antibodies were produced by immunizing Balb/C mice with cloned Alt a1 which is the major allergen of Alternaria alternata. Immunized spleen cells were fused with the Sp2/O mouse myeloma cell line using a hybridoma cloning kit. A clone with strong reactivity to cloned Alt a 1 was selected by ELISA and immunoblotting and compared with the ascites. Three batches of antibody harvests were made from the in vitro culture at intervals of 7 days while ascites were collected within 10 days. Results The average amount of antibody produced in vitro from the three harvests was 2.65mg/ml while the ascites gave 2.3mg/ml. The amount of antibodies from the three individual harvests was 3.11mg/ml; 3.78mg/ml and 1.37mg/ml collected on days 7, 14, and 21, respectively. The antibodies produced by both methods were able to recognize Alt a 1 in both ELISA and immunoblotting. Conclusions The findings suggest that the Mabs produced by in vitro method can reduce and/or eliminate the need for ascites induction

Dust mite allergens: mitigation and control.

In recent years, greater attention has been given to the role of indoor allergens as a cause of sensitization and allergic respiratory diseases. Although indoor allergen control measures to reduce symptoms in individuals allergic to mites have produced controversial results, environmental allergen avoidance is today one of the four primary goals of asthma management recommended in several guidelines of asthma treatment. Exposure to high indoor aeroallergen levels, especially to house dust mite allergens, is an important environmental risk factor for allergic sensitization and the subsequent development and exacerbation of asthma. Therefore, effective aeroallergen avoidance is of use to prevent and treat allergic diseases. Although endotoxin exposure may be protective in early life, it has been demonstrated that the inhalation of endotoxin may exacerbate asthma in house dust mite sensitized patients. Mite-allergic asthmatic patients should be aware of the dangerous combination of mite allergen exposure associated with high endotoxin levels in house dust. These two immunologically active substances have been associated with severe asthma and seasonal exacerbation of symptoms. Effective house dust mite allergen avoidance will never be achieved using a single control measure; various methods are required to affect the multiple factors that facilitate high indoor allergen levels. Education of the patients and their families is also an important component of environmental control strategies.

Inhalant Allergens as Risk Factors for the Development and Severity of Mild-to-Moderate Asthma in Hong Kong Chinese Children

Sensitization to aeroallergens has been found to be a dominant risk factor for asthma in population-based studies. Similar results in asthmatic children being managed in hospital-affiliated outpatient clinic have not been established. We therefore conducted a case-control study on asthmatic children attending a university hospital-based outpatient clinic to investigate the pattern of aeroallergen sensitization, and to assess the correlation between asthma control and the presence of allergen-specific IgEs. Asthmatic patients underwent a questionnaire assessment of their asthma control, skin prick tests (SPT) for allergen sensitization, and spirometric evaluation. Peripheral blood was collected from all subjects for in vitro serum specific IgE assay (RAST) to common aeroallergens. One hundred and seventy asthmatics (aged 9.8 ± 3.7 years) and 57 age-matched control subjects were enrolled. Our patients had a median of two asthmatic attacks within 6 months prior to evaluation, and their median Disease Severity Score was 13. The median FEV1 in our asthmatic children was 98%, whereas serum logarithmic total IgE concentrations in patients and controls were 2.57 and 2.09, respectively (p<0.0001). More than 85 % of our asthmatic children were sensitized to house-dust mite (HDM), and sensitization to HDM and cat, as well as elevated serum total IgE concentration, was a significant risk factor for the development of asthma in this cohort. Several objective measures of asthma severity, as well as FEV1, correlated significantly with sensitization to HDM, pets, and cockroaches. In conclusion, indoor aeroallergens are one of the risk factors for the development and severity of mild-to-moderate asthma in Chinese children in Hong Kong.