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Fungal extracellular polysaccharides in house dust as a marker for exposure to fungi: relations with culturable fungi, reported home dampness, and respiratory symptoms.

BACKGROUND: Epidemiologic studies have demonstrated an association between indoor fungal growth and respiratory symptoms. However, in only a few studies was fungal exposure actually measured. OBJECTIVE: The purpose of this study was to evaluate the measurement by enzyme immunoassay of extracellular polysaccharides of Aspergillus and Penicillium species (EPS-Asp/Pen ) in house dust as a marker for fungal exposure and to study the relations between EPS-Asp/Pen levels and home dampness and respiratory symptoms in children. METHODS: Extracts of house dust samples from bedroom and living room floors and mattresses from homes of 31 children with chronic respiratory symptoms and 29 children with no chronic respiratory symptoms were analyzed for EPS-Asp/Pen. RESULTS: EPS-Asp/Pen were readily detectable (40 to 46,513 nanogram equivalent/g dust) in 161 house dust extracts, with highest concentrations in living room floor dust. EPS-Asp/Pen levels were 2 to 3 times higher on carpeted floors than on smooth floors. EPS-Asp/Pen were significantly correlated with total culturable fungi (r = 0.3 to 0.5) and with house dust mite allergens (r = 0.3 to 0.5). EPS-Asp/Pen levels in living room floor dust were positively associated with occupant-reported home dampness. This was not observed for EPS-Asp/Pen in bedroom floor and mattress dust. EPS-Asp/Pen levels in living room floor dust were positively associated with respiratory symptoms. EPS-Asp/Pen in bedroom floor and mattress dust showed a reversed association with respiratory symptoms, possibly because of allergen-avoidance measures taken in the bedroom. CONCLUSION: The enzyme immunoassay for fungal EPS-Asp/Pen may be a useful method for exposure assessment of indoor fungi.

Antigens, Fungal↗

Assessing cow comfort: effects of two floor types and two tie stall designs on the behaviour of lactating dairy cows.

Our objective was to test the effects of two types of stall flooring and two tie stall designs on the behaviour of dairy cows. Using two cross-over designs, 16 lactating Holstein cows were housed for 3-week periods in each of four tie stalls to compare the effects of concrete versus mattress flooring, and a narrow versus a wide stall front opening. When cows were housed on a mattress flooring they increased their total lying time by 1.8h per day (51.0 versus 43.4% time per day). The duration of individual lying bouts was longer on concrete flooring (78 versus 62min) and the same was true for the duration of individual bouts of standing (80 versus 48min). On mattress flooring cows stood up and lay down more often than on concrete (28 versus 20 per day, respectively). On concrete cows spent more time standing without eating (35.2 versus 28.1% of sampling observations). Cows consistently made use of the additional space provided with the wide stall front opening, placing their head in the manger area during 70.6% of lying observations compared to only 43.4% of observations in the narrow stall front. However, measures of general activity were not significantly different for the two stall designs. Cows spent similar amounts of time eating and consumed similar quantities of feed in all four tie stalls. Our results suggest a lack of comfort may be apparent in reduced time spent lying and a subsequent increase in time spent standing without eating. A lower frequency of standing and lying and an increase in the bout duration of lying suggests that cows on concrete flooring have difficulty standing up and lying down.

Journal Article↗

Biomechanical properties of four circumferential flexor tendon suture techniques.

PURPOSE: We introduce 2 interlocking circumferential flexor tendon suture techniques: the interlocking cross-stitch and the interlocking horizontal mattress repair and biomechanically tested them against 2 commonly used methods. METHODS: Thirty-two deep digital flexor tendons harvested from sheep hindlimbs were transected sharply. These were repaired without a core suture using 4 different circumferential repair techniques: group 1, simple running; group 2, cross-stitch; group 3, interlocking cross-stitch; group 4, interlocking horizontal mattress. All tendons were tested to failure at a distraction rate of 20 mm/min. Load to 2-mm gap formation, stiffness, load to failure, and method of failure all were assessed. RESULTS: The mean load to 2-mm gap formation was 22.8, 20.7, 20.0, and 26.1 N for groups 1, 2, 3, and 4, respectively. The mean stiffness was 7.6, 8.1, 8.7, and 10.1 N/mm, and the mean load to failure was 30.9, 42.1, 49, and 52.9 N for groups 1, 2, 3, and 4, respectively. There was no statistically significant difference between groups 2 and 3. Group 4, however, was statistically better than the others in all measured parameters (except group 3 in load to failure). CONCLUSIONS: The interlocking horizontal mattress was the best performer overall, with statistically greater loads to failure, 2-mm gap formation, and stiffness. This technique could be considered for use in any patient likely to begin an early postoperative finger mobilization program.

Animals↗

Mesh-sided cots--yet another potentially dangerous infant sleeping environment.

Two cases of accidental asphyxia involving an 11.5 month old boy and a 3.5 month old boy who each died after being trapped between the elastic mesh side of their cots and the cot mattress are reported. In both cases the original cot mattress has either been replaced or augmented by a less well fitting, thicker mattress. Particular problems that exist with these type of mesh sided cots are the potential for considerable stretching of the side of the cot admitting the relatively larger, poorly supported infant head, with elastic recoil of the mesh holding the head in potentially dangerous positions. To help determine whether accidental asphyxia has occurred, death scene examination in cases of sudden infant death during sleep should include reconstruction of the position of the body in the cot or bed, with careful examination of the structure of the cot/bed.

Asphyxia↗

Randomised controlled trial to evaluate a new double-layer air-cell overlay for elderly patients requiring head elevation.

A clinical investigation was conducted concerning the effects of a newly designed double-layer air-cell overlay in preventing the onset of pressure ulcers for patients with a Braden scale score of < or = 16, and who require a head-elevated position of 45 degrees or higher. A randomised controlled trial was undertaken involving 82 patients from a general hospital ward using one of the following three support surfaces: a double-layer air-cell overlay, a single-layer air-cell overlay or a standard hospital mattress. A significantly lower percentage of patients using the double-layer air-cell overlay developed pressure ulcers (3.4%) compared to 19.2% and 37.0% for those patients using the single-layer air-cell overlay and standard mattress respectively. Based on these findings, a double-layer air-cell overlay should be more effective in preventing the onset of pressure ulcers than either a single-layer air-cell overlay or a standard hospital mattress for subjects requiring head elevation.

Age Factors↗

Cost-effective management of pressure-relieving equipment in a large teaching trust.

A pressure area care equipment service was initiated in a large teaching trust (approximately 1000 beds). A stock of over 200 mattress overlays and replacements was purchased and a mattress coordinator was appointed. The coordinator supplies and retrieves pressure-relieving equipment to and from wards, monitors the equipment daily when in use and records all occurrences of malfunction and mismanagement. Out of hours, mattress provision is the responsibility of the night nursing service. Equipment purchase is guided by interpretation of published controlled trials and the Trust's internal data on equipment reliability. Maintenance support is provided on-site by a half full-time equivalent medical technical officer. This approach was associated with a reduction in cost to the Trust and a consistent reduction in pressure ulcer incidence in those areas of the Trust which use it (not in those who do not). The cost of approximately 157,000 Pounds per annum compares favourably with expenditures reported in the past for some other (generally smaller) trusts of the order of 500,000 Pounds to 900,000 Pounds for rental of pressure-relieving equipment alone.

Cost-Benefit Analysis↗

Asthma, mite sensitization, and sleeping in bunks.

BACKGROUND: Mattresses and bedding are the main reservoirs of house dust mites. OBJECTIVE: Subjects sleeping in the bottom bunk may be exposed to house dust particles detached from bedding of the top bunk. Our aim was to ascertain whether this exposure could influence the development of mite sensitization and/or allergic symptoms in these individuals. METHODS: Symptoms of allergic respiratory disease were recorded and mite skin tests performed in 94 consecutive bunk-sleeping subjects (47 pairs of siblings) from an outpatient allergy clinic. Levels of Der p I, Der f I, and Der II were determined by enzyme-immunoassay in 16 randomly selected bedding dust samples (8 pairs of bunks). RESULTS: Mite sensitization rate and prevalence of allergic respiratory disease were similar for the top-bed and bottom-bed groups, whereas prevalence of asthma was significantly higher in the latter. Mite sensitization was significantly associated with family atopy background, whereas other factors such as house pets, indoor smoke exposure or types of mattress or bunks were not. Der p I levels higher than 2 microg/g dust were found in 12 of the 16 mattresses and the median of the 8-bed-bottom group was over 10 microg/g. CONCLUSIONS: Sleeping in bunks constitutes a greater risk of developing asthma for subjects sleeping in the bottom bed. Bunk sleeping should be discouraged in families with an atopic background and sensitized subjects should use the top bed.

Adolescent↗

Effectiveness of and compliance to intervention measures in reducing house dust and cat allergen levels.

BACKGROUND: Allergic sensitization is a major risk factor in asthma. OBJECTIVE: To evaluate the effectiveness of and compliance to intervention measures in reducing levels of house-dust mite and cat allergen in the context of a randomized, controlled study in the primary prevention of asthma. METHODS: A total of 545 high-risk families were recruited prenatally and randomly assigned into the intervention group (n = 278) and the control group (n = 267). Intervention measures were instituted before birth of the infants and maintained for 12 months afterward in the intervention group and the control group received the usual care from their family physician. Dust samples were collected at six sites in the homes before birth and at specific intervals up to 24 months after birth for analysis of allergens. At 24 months, there were 244 families in the intervention group and 228 in the control group available for followup examination. RESULTS: House-dust mite avoidance measures, consisting of encasement of mattresses, pillows, and duvets, and hot-water washing of bedding were effective in reducing mite allergen in parents' mattresses to one-third from baseline, significantly lower than the control group, even at 24 months. The use of an acaricide did not reduce mite allergen levels in carpets and upholstered furniture. Seventeen intervention families gave up their cats but six families acquired a new one over a period of 24 months, similar to control families. Cat allergen levels decreased in all sites in the homes of those who removed the cat, similar in both groups. CONCLUSIONS: House-dust mite avoidance measures were effective in reducing house-dust mite allergen in mattresses, but not on floors. Reduction in cat allergen levels were evident for those families who got rid of their cats, but the advice to remove pets was not adhered to by most families.

Allergens↗

House-dust-mite allergen concentrations (Der f 1) and mold spores in apartment bedrooms before and after installation of insulated windows and central heating systems.

BACKGROUND: It has been hypothesized that changes in heating systems and insulation of homes in developed countries have generated an indoor climate favorable to organisms that excrete allergens inducing sensitization and allergic disease. The purpose of this study was to determine the influence of the installation of highly insulated windows and central heating systems on indoor climate, and mite-allergen (Der f 1) and mold spore concentrations. METHODS: The bedrooms of 98 apartments were examined before and 7 months (mean) after installation of insulated windows and central heating systems. The air-exchange rate, temperature, and humidity were measured. In settled dust on carpets and mattresses, the number of colony-forming mold spores and the Der f 1 concentration were determined. The inhabitants completed a questionnaire about their lifestyles and housing conditions. RESULTS: The air-exchange rate decreased from geometric mean 0.73 to 0.52 per hour (P=0.029). Temperature (mean 13.4 vs 17.5 degrees C, P<0.001), and absolute humidity (mean 4.6 g vs 6.2 g H2O/kg air, P<0.001) increased. Relative humidity remained nearly unchanged (mean 47.6 vs 49.1%). Der f 1 concentrations on carpets (geometric mean 0.65 vs 1.28 microg/g dust, P < 0.001) and mattresses (geometric mean 1.56 vs 2.40 microg/g, P=0.002) increased. Among the fungi that were analyzed, only the thermotolerant species Aspergillus fumigatus increased (geometric mean 20 vs. 60 colony-forming units/g carpet dust, P = 0.02). CONCLUSIONS: The findings of this study suggest that the installation of insulated windows and central heating systems is associated with an increase of Der f 1 concentrations in carpet and mattress dust and of A. fumigatus in carpet dust in apartment bedrooms.

Air Pollution, Indoor↗

The effect of high-efficiency and standard vacuum-cleaners on mite, cat and dog allergen levels and clinical progress.

The major triggers for allergic asthma are exposure to allergens of the house dust mite, Dermatophagoides pteronyssinus, and of pets. Unfortunately studies of techniques designed to reduce house dust mite and pet allergens have had mixed results. However, new so-called 'improved' products continue to appear on the market and require subjective evaluation. The homes of 60 house dust mite-allergic patients were studied to compare the effects of high-efficiency and standard vacuum-cleaners on allergen concentration. Der p 1 (house dust mite), Fel d 1 (cat) and Can f 1 (dog) allergens were measured in four separate locations in each home. Clinical analysis was by lung function, bronchodilator usage and histamine challenge techniques. There was a significant reduction in Fel d 1 (ng/m2) in dust samples from the living-room carpet (p = 0.046), bedroom carpet (p = 0.003) and mattress (p = 0.013) and living-room sofa (p = 0.005) after 12 months of using the high-efficiency cleaners, but only in the mattress sample using the standard cleaners (p = 0.014). Can f 1 (ng/g dust) was reduced in the mattress sample after using the high-efficiency vacuum-cleaners (p = 0.028), but not at other sites. Der p 1 levels were not significantly changed over this period. Clinically, patients in the high-efficiency group showed improvements in peak expiratory flow rate (PEFR) (p = 0.004), FEV1 (p = 0.026) and bronchodilator usage (p = 0.005) after 12 months. When the cat-sensitive patients were analyzed separately, improvements in histamine PC20 (p = 0.039) were also seen. Reducing Fel d 1 concentrations, in the absence of any change in Der p 1 concentrations, can produce significant improvements in the lung function of atopic, asthmatic patients. This effect was primarily achieved in those patients with cat sensitivity, but who did not possess a cat themselves.

Adolescent↗

Do mite avoidance measures affect mite and cat airborne allergens?

BACKGROUND: Effective mite allergen avoidance measures are presumed to reduce airborne allergens yet the quantity in the air is rarely measured. OBJECTIVE: To monitor airborne allergen during a placebo-controlled mite allergen avoidance study. METHODS: Bedrooms of 56 atopic asthmatic children were randomly allocated to hot washing and encasing covers + acaricide (active regime) or placebo treatment. Dust was collected from the mattress, bedding and carpets; airborne allergen was measured using Casella samplers and dust settling in open Petri dishes. Der p 1, Der p 2 and Fel d 1 were measured. RESULTS: After 24 weeks of mite allergen avoidance the Casella air-samplers collected Der p 1 less frequently in active than placebo-treated bedrooms (0 vs. 29%, P<0.05) and Petri dishes in the active group collected less than baseline (0.2 vs. 0.6 ng/day P<0.05). Homes without cats had less cat allergen than cat-owning homes and when actively treated for 24 weeks showed a greater reduction (P = 0.03) in mattress cat allergen than the placebo group. CONCLUSION: Encasing covers and hot washing of bed linen reduced mite aeroallergen (and mattress cat allergen in the absence of cats). This could mean dual benefits to a patient sensitive to both mite and cat.

Air Pollutants↗

Inverse correlation of domestic exposure to Dermatophagoides pteronyssinus antigen patch test reactivity in patients with atopic dermatitis.

BACKGROUND: In recent years considerable interest in the pathogenetic role of aeroallergens exacerbating atopic dermatitis (AD) has emerged. The 'atopy patch test' with aeroallergens was introduced by Platts-Mills et al. as an experimental model and as a diagnostic tool. However, its relevance for the clinical manifestation of AD is still not clear. OBJECTIVE: We asked whether there is a relationship between the individual antigen exposure to the major allergen of Dermatophagoides pteronyssinus (Der p 1) and the immunological markers of sensitization to Der p 1 or the clinical severity of AD. METHODS: We investigated 92 patients with moderate to severe AD. For clinical evaluation the SCORAD severity score was used. Patch tests were performed with purified Der p 1. Specific IgE was measured by a commercial assay. Der p 1 exposure was quantified in a sample of the patient's mattress dust by using a commercial ELISA. RESULTS: No correlation between SCORAD, Der p 1 exposure and RAST could be established. However, there was an unexpected significant inverse correlation between the quantity of mite antigen in the mattress dust and patch test reactivity. Patients with a high antigen load (> 25 microg/g) mostly had a negative patch test. Also, when Der p 1 was correlated to the mattress area (m2) in this group all patch tests were negative. A possible explanation could be that continuous exposure of the skin to house dust mite allergen Der p 1 may induce a down-regulation of the skin immune system of patients with AD. CONCLUSION: Although the mechanism of this phenomenon is presently unknown, our study shows that a positive allergen patch test alone should not be an indication to undertake allergen exclusion measures in AD patients.

Adolescent↗

Window pane condensation and high indoor vapour contribution - markers of an unhealthy indoor climate?

OBJECTIVE: The aim of this study was to investigate whether window pane condensation and indoor vapour contribution >/= 3 g/m3 could be used as indicators of defective air change rate, high indoor humidity and high mite allergen concentration in mattress dust. METHODS: Actual ventilation rate, indoor temperature, air humidity (AIH/RH) and concentrations of mite allergen were measured in 59 houses and compared with received outdoor temperatures and air humidity. Indoor vapour contribution defined as the difference between the indoor and the outdoor vapour concentration was calculated. Sensitivity, specificity, predictive values and accuracy were calculated for window pane condensation and high vapour contribution (>/= 3 g/m3), as indicators of defective ventilation (< 0.5 ACH), high indoor humidity (>/= 7 g/kg and >/= 45% RH) and high mite allergen concentration in mattress dust (>/= 2 microg/g). RESULTS: All houses with high humidity and high mite allergen concentrations were positive for the two indicators (high sensitivity), but with a specificity of only 50% so that half of the houses with reported condensation and high vapour contribution turned out to be low pollution houses with adequate high ventilation levels. Both indicators had high negative predictive values and absence of the two indicators almost certainly (97-100%) excluded high indoor pollution with high humidity and high mite concentrations. Overall more than 70% of the dwellings were correctly classified by the two indicators. CONCLUSION: Absence of window pane condensation on double-glazed windows and low indoor vapour contribution (< 3 g/m3) during the winter are true markers of a dwelling without high indoor air humidity and without high mite allergen concentrations in mattress dust in houses in a cold temperate climate with subzero outdoor temperatures. The presence of the two indicators is associated with a 18-45% risk of high humidity and mite allergen concentrations so in this latter group further measurements are needed for correct classification.

Air Pollution, Indoor↗

Exposure to endotoxin or other bacterial components might protect against the development of atopy.

BACKGROUND: Several recent studies have shown that growing up on a farm confers significant protection against the development of atopy. These findings point particularly towards the importance of exposure to stable dust and farm animals. It has furthermore been reported that endotoxin, an intrinsic part of the outer membrane of gram negative bacteria, is abundant in environments where livestock and poultry is kept. The aim of this study was therefore to measure the level of environmental endotoxin exposure in homes of farmers' children, children with regular contact to livestock and control children with no contact to farm animals. METHODS: Eighty-four farming and nonfarming families were identified in rural areas in Southern Germany and Switzerland. Samples of settled and airborne dust were collected in stables, and of settled dust indoors from kitchen floors and the children's mattresses. Endotoxin concentrations were determined by a kinetic Limulus assay. RESULTS: Endotoxin concentrations were highest in stables of farming families, but were also significantly higher indoors in dust from kitchen floors (143 EU/mg vs 39 EU/mg, P < 0.001) and children's mattresses (49479 EU/m2 vs 9383 EU/m2, P < 0.001) as compared to control children from nonfarming families. In addition, endotoxin levels were also significantly higher in mattresses and dust from kitchen floors in households where children had regular contact to farm animals (38.6 EU/mg and 23340 EU/m2, respectively) as compared to control subjects. CONCLUSION: We propose that the level of environmental exposure to endotoxin and other bacterial wall components is an important protective determinant for the development of atopic diseases in childhood.

Adolescent↗

[Exposition and sensitisation to indoor allergens, house dust mite allergen and cat allergens].

The study examined the exposure to biological indoor air agents and their possible role for allergies and respiratory tract illnesses of children. It was conducted as a case control study (atopic vs non-atopic children) at the four surveillance public health departments in Baden-Württemberg in the winter season 1999/2000 and included 379 children of the fourth class. The concentrations of the house dust mite antigens Der F1, Der p1, and Der Gr2 as well as cat allergen Fel d1 were determined in the children's bedrooms on the ground and in the mattress. Specific IgE-antibodies against allergens from house dust, mites and cat were determined in the serum of the children. For mite allergens the following medians ( micro g/g) were estimated in floor dust: Der p1 = 0.6, Der f1 = 2.3, Gr2 = 0.1; in mattresses: Der p1 = 1.2, Der f1 = 3.4, Gr2 = 0.3. The median of Fel d1 in floor dust was 0.2 microg/g, in mattresses 0.1 microg/g. Sensitisation to dust mite allergen was found to be more prevalent than sensitisation to cat. The distribution of sensitisation among the cases and controls is different. Among the cases, more subjects were sensitised to dust mites (32.9 %) and cat (13.1 %). Among the controls, 17.1 % were sensitised to dust mites and 4.1 % to cat. The results showed no direct association between the prevalence of allergies or respiratory tract illnesses and the indoor concentrations of the allergens. Possible reasons for these findings are discussed.

Allergens↗

Evaluation of impermeable covers for bedding in patients with allergic rhinitis.

BACKGROUND: Encasing bedding in impermeable covers reduces exposure to house-dust mites, but the clinical benefit of this intervention as part of mite-avoidance measures for patients with allergic rhinitis is not known. We performed a multicenter, randomized, placebo-controlled trial of one year of use of impermeable bedding covers in the bedrooms of patients with rhinitis who were sensitized to house-dust mites to determine the effects on the signs and symptoms of disease. METHODS: Three participating university medical centers enrolled 279 patients with allergic rhinitis who were randomly assigned to receive impermeable or non-impermeable (control) covers for their mattress, pillow, and duvet or blanket. At the start of the study, all participants received information on general allergen-avoidance measures. The severity of rhinitis was measured on a rhinitis-specific visual-analogue scale and by means of a daily symptom score and nasal allergen provocation testing. We also measured the concentrations of Dermatophagoides pteronyssinus (Der p1) and D. farinae (Der f1) in dust from patients' mattresses, bedroom floors, and living-room floors at base line and after 12 months as a measure of the efficacy of the intervention. RESULTS: A total of 232 patients completed the study. There was a significant reduction in Der p1 and Der f1 concentrations in the mattresses of the impermeable-cover group, whereas there was no significant reduction in the control group. However, there was no significant effect on the clinical outcome measures. Analyses of subgroups defined according to age, level of exposure, type and severity of sensitization, or characteristics of the patient's home had similar results. CONCLUSIONS: Mite-proof bedding covers, as part of a structured allergy-control program, reduced the level of exposure to mite allergens. Despite the success of the intervention, this single avoidance measure did not lead to a significant improvement of clinical symptoms in patients with allergic rhinitis.

Adolescent↗

Current mite, cat, and dog allergen exposure, pet ownership, and sensitization to inhalant allergens in adults.

BACKGROUND: Simultaneous exposure to more than one allergen might modify the effect of individual allergens. OBJECTIVE: The purpose of this study was to investigate the effect of current exposures to mite, cat, and dog allergen and pet ownership on sensitization in adults. METHODS: Questionnaires, skin tests, and home visits (Der p 1, Fel d 1, and Can f 1, ELISA; mattresses, living room floors) were performed in 2502 adults. Allergen exposure was treated as a continuous variable and divided into quartiles. To investigate the interaction between allergens, quartiles for 3 allergens were added, creating arbitrary combined exposure categories. RESULTS: In the univariate analysis, mite sensitization was associated with Der p 1 in mattresses (odds ratio [OR], 1.10; 95% CI, 1.01 to 1.19; P =.03) and with Can f 1 in living room floors (OR, 1.08; 95% CI, 1.00 to 1.17; P =.05). In a multivariate regression analysis, Der p 1 in mattresses remained an independent associate of mite sensitization (OR, 1.12; 95% CI, 1.02 to 1.23; P =.03) and pollen sensitization (OR, 1.23; 95% CI, 1.11 to 1.36; P =.0001). The proportion of subjects sensitized to mite increased significantly with the increasing combined exposure categories (P <.0001). The highest prevalence of sensitization to cat and dog was in the medium combined exposure categories. Cat ownership was associated with a reduced prevalence of sensitization to cats (P =.002) and a reduced prevalence of sensitization to dog (P =.003) but had no effect on sensitization to mite and pollen. CONCLUSIONS: Sensitization to dust mites increased with the increasing combined exposure. Cat ownership was associated with a lower prevalence of sensitization to cat and dog but not to mite and grass pollen.

Administration, Inhalation↗

House dust mite allergen levels in German day-care centers.

We investigated the levels of the major house dust mite allergens, Der p 1 and Der f 1, in dust collected from various locations in 41 day-care centers from two German cities (Düsseldorf and Bonn). One hundred and thirty-seven (96%) of 143 samples yielded detectable amounts of house dust mite allergen (range, < 15-85,000 ng/g; interquartile range, 210-1,480 ng group I allergen [sum of Der p 1 and Der f 1]/g dust), and 24 (17%) of the samples (8/34 mattresses; 11/46 cushions/soft toys; 5/43 carpeted floors, 0/20 smooth floors) exceeded the proposed "threshold" level of 2,000 ng/g dust in 18 (44%) of 41 day-care centers. Der p 1 and Der f 1 could be detected in nearly an equal number of samples. The highest concentrations of house dust mite allergens were found in dust from mattresses (geometric mean, 1,103 ng/g dust) and cushions/soft toys (geometric mean, 1,004 ng/g dust). The allergen load per unit area from carpeted floors exceeded that from smooth floors by more than two orders of magnitude. In comparison with dust samples from private homes within the same geographical area, the mite allergen levels in mattress dust (RR, 0.34; CI95, 0.18-0.64) and floor dust (RR, 0.21; CI95, 0.09-0.49) from day-care centers were significantly lower (p < 0.001). We conclude that day-care centers should be included as potential places of additional exposure to house dust mite allergens if avoidance measures are taken.

Allergens↗