Airborne cat allergen reduction in classrooms that use special school clothing or ban pet ownership

BACKGROUND: Allergens from furred animals are brought to school mainly via clothing of pet owners. Asthmatic children allergic to cat have more symptoms when attending a class with many cat owners, and some schools allocate specific resources to allergen avoidance measures. OBJECTIVE: The aim of the current study was to evaluate the effect of school clothing or pet owner-free classes compared with control classes on airborne cat allergen levels and to investigate attitudes and allergic symptoms among the children. METHODS: Allergen measurements were performed prospectively in 2 classes with school clothing, 1 class of children who were not pet owners, and 3 control classes during a 6-week period in 2 consecutive years. Portable pumps and petri dishes were used for collection of airborne cat allergen, and a roller was used for sampling on children's clothes. Cat allergen (Fel d 1) was analyzed with enzyme-linked immunoassay and immunostaining. Both years, questionnaires were administered to the children. RESULTS: We found 4-fold to 6-fold lower airborne cat allergen levels in intervention classes compared with control classes. Levels of cat allergen were 3-fold higher on clothing of cat owners than of children without cats in control classes. Pet ownership ban seemed less accepted than school clothing as an intervention measure. CONCLUSION: For the first time, it has been shown that levels of airborne cat allergen can be reduced by allergen avoidance measures at school by using school clothing or pet ownership ban, and that both measures are equally efficient. The clinical effect of these interventions remains to be evaluated.     

Cat allergen (Fel d 1) levels on school children's clothing and in primary school classrooms in Wellington, New Zealand

Background: New Zealand has a high prevalence of the major allergic diseases including asthma, rhinitis, and eczema, and cat ownership is common, with more than 50% of homes containing a cat. Objective: The study was designed to examine the levels of cat allergen (Fel d 1) in the primary school environment, both on floors and on children's clothing. Methods: We collected and analyzed dust samples from 11 school classrooms and from 202 children's garments using vacuum sampling and two-site monoclonal antibody ELISA, respectively. Environmental variables were identified by questionnaire. Results: The geometric mean level of Fel d 1 in classrooms was 2.61 μ/gm (95% confidence interval, 1.28 to 3.84); however, seven classrooms had a floor sample with Fel d 1 greater than 8 μg/m². Carpeted floor levels at 2.21 μg/gm (1.28 to 3.84) were considerably higher than those on uncarpeted floors, at 0.33 μg/gm (0.1 to 1.14). Floor levels and pupil cat ownership rates were positively correlated (r²= 0.93, p = 0.0003). Children from homes with cats carried allergen on their clothes (mean Fel d 1, 6.10 μg per garment compared with non-cat owners (0.72 μg per garment). Wool and polyester garments contained more Fel d 1 than cotton clothing. Girls' clothing had significantly higher levels of allergen than did that of boys, even after controlling for cat status and fabric differences. Conclusions: Carpeting should be discouraged in environments such as schools and child care centers, where children spend considerable time. Transport of Fel d 1 on clothing from the domestic to the school environment is a major source of classroom cat allergen. (J Allergy Clin Immunol 1997;100:755-9.)     

School as a risk environment for children allergic to cats and a site for transfer of cat allergen to homes

BACKGROUND: Many children are allergic to furred pets and avoid direct pet contact. The school may be a site of indirect exposure to pet allergens, which may induce or maintain symptoms of allergic diseases. OBJECTIVE: We sought to investigate airborne levels of cat allergen (Fel d 1) at schools and in homes with or without cats and to study clothes as a route for dissemination of allergens between homes and school. METHODS: Airborne cat allergen was collected with personal samplers from (1) children attending classes with many (>25%) or few (<10%) cat owners and (2) homes with or without cats. A recently developed amplified ELISA assay, which detects low levels of airborne cat allergen in pet-free environments, was used. Dust samples were collected from clothes and mattresses. RESULTS: There was a 5-fold difference in the median levels of airborne cat allergen between classes with many and few cat owners (2.94 vs 0.59 ng/m3; P <.001). The median airborne cat allergen concentration in classes with many cat owners was significantly higher than that found in the homes of non-cat owners (P <.001) but lower than that found in homes with cats (P <.001). Allergen levels in non-cat owners' clothes increased after a school day (P <.001). Non-cat owners in classes with many cat owners had higher levels of mattress-bound cat allergen (P =.01). CONCLUSION: The results indicate significant exposure to cat allergen at school. Allergen is spread through clothing from homes with cats to classrooms. There the allergen is dispersed in air and contaminates the clothes of children without cats. The allergen levels in non-cat owners' homes correlate with exposure to cat allergen at school.     

Cat allergen level: its determinants and relationship to specific IgE to cat across European centers

BACKGROUND: Cat allergen level in settled house dust and its determinants in Europe are unknown. OBJECTIVE: The aim of this study is to quantify the level of cat allergens in mattress dust, to study its determinants, and to analyze the relationship with cat specific IgE on community level across European centers. METHODS: Trained field workers collected dust from approximately 3000 mattresses during home visits in 22 European Community Respiratory Health Survey II centers. Sieved dust extracts were assayed for cat allergen using a mAb ELISA assay. RESULTS: The overall geometric mean cat allergen was 0.94 microg/g, ranging from 0.12 microg/g in Huelva, Spain, to 3.76 microg/g in Antwerp, Belgium. Current cat owners' homes showed substantially higher levels than past cat owners' and never cat owners' homes (geometric mean and 95% CI, 61.4 microg/g [48.4-77.9] vs 1.37 microg/g [0.97-1.9] vs 0.29 microg/g [0.27-0.31]). Community prevalence of cat ownership was moderately correlated with cat allergen levels in noncat owners (r(s) = 0.50), but not for past or current cat owners. The multilevel model identified community prevalence of cat keeping as the only statistically significant determinant of mattress cat allergen levels for noncat owners. However, averaged cat allergen levels per center were not related to community prevalence of detectable specific IgE to cat. CONCLUSION: Not having a cat in the home is associated with substantially lower Fel d 1 concentration, but does not protect against high Fel d 1 exposure in communities where cat ownership is common. CLINICAL IMPLICATIONS: People (including patients with cat allergy) who do not own cats may be exposed to high levels of cat allergen in their home, particularly if they live in communities with high levels of cat ownership.     

Comparison of four allergen-sampling methods in conventional and allergy prevention classrooms

BACKGROUND: Several allergen-sampling methods are used to assess level of personal or indirect exposure to cat in homes, schools and other public buildings and working environments. OBJECTIVE: To compare four different allergen-sampling methods (dust collectors, Petri dishes, person-carried pumps and intranasal samplers) by simultaneous sampling in classrooms and to compare the cat allergen levels between conventional classrooms and allergy prevention classrooms. Another aim was to relate the results to self-reported frequency of allergy and asthma symptoms among the children, to their perception of the school environment. METHODS: Among all compulsory schools (n = 257) in the Stockholm suburban area, 35 classrooms (five with implemented allergy prevention measures, seven with additional cleaning and 23 with normal cleaning routines) were chosen for allergen-sampling. Dust collectors (two models), Petri dishes, person-carried pumps and intranasal samplers were used simultaneously. All children (n = 829) received a self-administered questionnaire which included questions about home and school environment, allergic disease, asthma symptoms and pet contact. RESULTS: The correlation between sampling methods was generally poor.Furthermore, there was no significant difference in allergen levels between allergy prevention and allergen avoidance classes compared to conventional classes. Median levels were generally, but not significantly, lower in classes with few cat owners, compared to classes with many cat owners. Children in allergy prevention classes were more satisfied with the indoor air quality and cleaning than children attending classes with fewer or no allergy prevention measures (P < 0.0001). Nine per cent of all children reported allergic symptoms while at school. CONCLUSION: The lack of correlation between sampling methods used simultaneously demonstrates the difficulty in assessing allergen levels in schools and similar environments. The implemented intervention measures (allergy prevention/allergen avoidance) did not influence cat allergen levels at school.     

Allergen avoidance does not alter airborne cat allergen levels in classrooms

BACKGROUND: Some schools in Sweden offer allergen avoidance classrooms for allergic children with severe asthma. However, the measures commonly used to achieve a reduction in allergen levels have not been properly evaluated. The aim of the present prospective study was to study whether the levels of airborne cat allergen are altered after introducing feasible intervention measures in classrooms, without interfering with peoples' freedom of choice regarding pet ownership. METHODS: Twenty-five classes, including five established allergy prevention classrooms participated in the study during a school year. After one term, six classes underwent a number of intervention measures recommended by the Swedish National Institute of Public Health. Curtains, upholstery and plants were removed, bookshelves were replaced with cupboards and regular cleaning was increased. Airborne dust was collected weekly (32 weeks) using duplicate Petri dishes (n = 1574) and on six occasions using two personal air samplers in each class (n = 264). RESULTS: Airborne cat allergen levels were showing a similar variability throughout the whole study in all classes. Despite extensive measures in order to reduce allergen exposure, cat allergen levels were unaltered in the six classes after intervention. Allergen levels were not significantly lower in the established allergy prevention classes, compared with the other classes. Cat allergen levels differed, however, significantly between classes with few and many cat owners (P < 0.05). CONCLUSIONS: We conclude that the recommended allergen avoidance measures used in this study did not reduce airborne cat allergen. It seems plausible that measures that fail to reduce allergen levels also fail to influence health status in allergic children but this remains to be shown.     

Fel d 1 and Can f 1 in settled dust and airborne Fel d 1 in allergen avoidance day-care centres for atopic children in relation to number of pet-owners, ventilation and general cleaning

BACKGROUND: Special day-care centres for atopic children have been established in Sweden. OBJECTIVE: To study concentrations of cat (Fel d 1) and dog (Can f 1) allergens in settled dust and airborne cat allergen in day-care centres in relation to pet ownership among children and staff, ventilation and general cleaning. METHODS: Twelve allergen avoidance day-care centres and 22 conventional day-care centres were included in the study. Settled dust was collected and analysed with ELISA. Airborne cat allergen levels were measured in eight allergen avoidance and seven conventional centres with a personal air sampler and analysed with an amplified ELISA. Air change rate per hour (ACH) was measured. A questionnaire which focused on keeping of cat and dog among staff and children and frequency of general cleaning was used. RESULTS: In the allergen avoidance day-care centres neither children nor staff reported ownership of cats or dogs, compared with 21/22 of the conventional centres in which children and staff kept furred animals. Fel d 1 and Can f 1 were found in settled dust in all day-care centres. In the allergen avoidance compared with the conventional centres the concentrations of Fel d 1 and Can f 1 were lower, Fel d 1: median 0. 64 microg/g vs 5.45 microg/g and Can f 1: 0.39 microg/g vs 2.51, both P < 0.001, and airborne Fel d 1 was also lower in the allergen avoidance centres compared with the control centres, 1.51 ng/m3 vs 15.8 ng/m3, P = 0.002. A correlation was found between airborne and settled Fel d 1, rs = 0.75, P < 0.001. Furthermore, a correlation was found between increased ACH and decreased levels of Fel d 1 in the air in the day-care centres with no cat-owners, rs = - 0.86, P = 0.007. No relation was found between levels of cat or dog allergen and amount of general cleaning. CONCLUSION: Not keeping pets seems to reduce children's exposure to pet-allergen in their 'working environment'. Additionally, appropriate ventilation seems to reduce Fel d 1 in the air in day-care centres.     

Exposure to mite and cat allergens on a range of clothing items at home and the transfer of cat allergen in the workplace

BACKGROUND: Clothing has been proposed as an additional source of exposure to mite and cat allergens. Dispersal of allergen into public places has also been attributed to clothing. OBJECTIVES: We sought to study the contribution of various types of clothing on mite and cat exposure in a domestic environment. Also, we studied the ability of clothing to transfer allergen in a workplace. METHODS: Personal exposure to mite and cat allergen from a range of clothing was measured by using intranasal air samplers in 11 homes. Five categories of clothing were tested. Wearing no upper clothing was the sixth category tested to distinguish the contribution of clothing over ambient background exposure. An adhesive tape was used to sample allergen from the surface of clothing, and reservoir dust samples were also collected. The above techniques were also used in the workplace to examine the amount of cat allergen transferred from cat owners to non-cat owners. RESULTS: The amount of mite and cat allergen inhaled differed among the clothing types worn and whether they had been washed recently. Wearing a woolen sweater increased personal allergen exposure to cat and mite allergen by a mean of 11 and 10 times, respectively. Clothing items that were less frequently washed carried more allergen whether assessed by vacuuming or sampled with adhesive tape. This corresponded to the amount of allergen inhaled. We also found that cat levels on non-cat owners' clothing increased significantly at the end of a working day, which lead to the increase in their personal allergen exposure to cat. CONCLUSIONS: These studies strongly support the emerging model that personal clothing is an important source of both mite and cat allergen exposure. This article also demonstrates the importance of clothing as a means of distributing cat allergen into cat-free environments.     

Longitudinal study on the relationship between cat allergen and endotoxin exposure, sensitization, cat-specific IgG and development of asthma in childhood--report of the German Multicentre Allergy Study (MAS 90)

BACKGROUND: Controversial data have emerged regarding the question whether cat exposure in childhood favours or decreases the risk of sensitization and allergic airway disease. In a prospective birth-cohort study, we assessed the association between longitudinal cat allergen exposure, sensitization (immunoglobulin E, IgE), IgG antibody (ab) levels to cat and the development of asthma in children up to the age of 10 years. METHODS: Of 1314 newborn infants enrolled in five German cities in 1990, follow-up data at age 10 years were available for 750 children. Assessments included yearly measurements of specific serum IgE to cat and at age 6 and 18 months, 3, 4 and 10 years measurement of cat allergen Fel d 1 in house dust samples. Additionally, Fel d 1-specific IgG ab were determined in 378 serum samples of 207 children. Endotoxin exposure in mattress dust was measured in a subgroup of 153 children at age 10 years. From age 4 years on, International Study of Asthma and Allergy in Childhood (ISAAC) questionnaires were completed yearly in order to assess the prevalence of wheeze and asthma. RESULTS: Serum IgG-levels to cat showed a large variation, however, intraindividually values showed rather constant concentration over a longer time period. The IgG levels at school-age correlated with cat allergen exposure during the first 2 years of life. Specific IgE to cat was clearly associated with wheeze ever, current wheeze and bronchial hyperresponsiveness (BHR), this was also observed for children with specific IgE ab to cat (>0.35 kU/l) plus IgG levels above 125 U/ml. A large percentage of very highly exposed children showed high IgG but no IgE responses to cat, however, not all highly exposed children were found to be protected from sensitization. Children with IgG but without IgE ab to cat showed the lowest prevalence of wheeze ever and current wheeze despite high cat allergen exposure, however, this trend did not achieve significance. While homes of cat owners showed higher Fel d 1 concentrations than homes without cats, homes of cat owners were not found to have higher endotoxin levels in carpet dust samples than homes without cats. CONCLUSIONS: We could confirm that high cat allergen exposure in a cohort with lower community prevalence of cats is associated with higher serum IgG and IgE levels to cat in schoolchildren. Sensitization to cat allergen (IgE) is a risk factor for childhood asthma. While exposure to cat allergen during infancy is associated with sensitization (IgE), only in the very highly exposed children the likelihood of sensitization (IgE) is decreased and high IgG levels to cat without IgE were associated with low risk of wheeze. However, cat-specific IgG ab levels did not protect children with IgE-mediated sensitization from wheeze.     

Human hair: an unexpected source of cat allergen exposure

BACKGROUND: Cat allergens are ubiquitous because the clothing of cat owners constitutes an important source of distribution of Fel d 1 in cat-free environments. Since Fel d 1 can adhere to a variety of surfaces, we sought to verify if human hair belonging to individuals with or without a cat at home might represent a reservoir and be a possible carrier of cat allergens. METHODS: Seventy-three women (25 with a non-neutered male cat and 25 with a dog at home, and 23 controls without any direct contact with these animals) were recruited. The collection of material from hair was carried out using a modified version of a battery-powdered portable sampler. Particulate material was harvested onto glass fiber filters (25 mm in diameter, with a pore size of 2 microm; AP 20 Millipore, Milan Italy), extracted in phosphate buffer with BSA and then assayed for the evaluation of cat allergen using an ELISA based on anti-Fel d 1 monoclonal antibody. RESULTS: Detectable levels of cat allergen were found in 2 controls, in 2 women with a dog at home and in 13 women with a cat at home, respectively. CONCLUSIONS: In some women with a cat at home, hair constitutes a significant reservoir of Fel d 1. It is likely that these amounts of cat allergen might contribute to allergic sensitization when released in cat-free environments.     

Fel d 1 production in the cat skin varies according to anatomical sites

BACKGROUND: Fel d 1 is the major cat allergen, inducing asthma in sensitized individuals. It is produced by the skin and lies on fur. Recently, it was established that the amount of Fel d 1 on fur varies among anatomical sites. However, it is not known whether the allergen production by skin varies in parallel. The objective was to compare the Fel d 1 production by male cat skin in two anatomical sites, the face and the chest, in order to correlate it with Fel d 1 amounts on fur, and to assess the reaccumulation of Fel d 1 after washing. METHODS: Ten intact male cats were shaved under general anesthesia at both areas, and the fur was collected. The skin was washed and the washing fluid collected for Fel d 1 assays. Fel d 1 levels were measured in microg/g fur and ng/cm2 skin by ELISA before and after washing and 48 h later. RESULTS: In skin washing, the mean Fel d 1 level was significantly higher in the face (1015.2 +/- 821.6 ng/cm2) than the chest (115.2 +/- 66.8 ng/cm2). In the fur, the respective levels were 63.6 +/- 34 and 29.6 +/- 13.6 microg/g. In the skin sample taken after skin washing, the level of Fel d 1 dropped to 25.1 +/- 25.7 ng/cm2 on the face and to 22 +/- 17.4 ng/cm2 on the chest. After 2 days, skin Fel d 1 levels returned to basal values, with higher values on the face than the chest. CONCLUSIONS: This study shows that Fel d 1 levels on the skin are dramatically higher on the facial area than chest. This anatomical variation is concordant with the levels of Fel d 1 found on fur. Washing reduces levels of major allergen on cat skin and fur, but the accumulation on skin is restored within 2 days.     

Focus on cat allergen (Fel d 1): immunological and aerodynamic characteristics, modality of airway sensitization and avoidance strategies

The increasing frequency of pet ownership (especially cats) in many industrialized countries has raised the level of exposure to the allergens produced by these animals. Moreover, it is likely that modern energy-saving systems and the wide use of upholstered furniture has resulted in closer contact between cats (and their allergens) and humans. Many different methods have been developed to quantify the main cat allergen (Fel d 1) in settled dust and in ambient air. The threshold levels of cat allergen inducing sensitization or triggering respiratory symptoms in sensitized patients have been calculated in settled dust, but airborne amounts of Fel d 1 probably represent a more reliable index of allergen exposure. Noticeably, the amount of Fel d 1 may be relatively high also in confined environments where cats have never been kept. It has been demonstrated that clothes of cat owners are the main source for dispersal of allergens in cat-free environments. This fact may be of relevance, because recent studies have shown that allergic sensitization to cats is more likely to develop in children exposed to moderate levels of this allergen than in children exposed to high amounts of Fel d 1. The ubiquity of cat allergen may justify the common observation that allergen avoidance is often insufficient to reduce the risk of developing allergic sensitization and/or symptom exacerbation in highly susceptible patients. Further efforts are needed to improve the efficacy of Fel d 1 avoidance strategies to try to reduce the risk of allergic sensitization to this allergen.     

Detection of an allergen in dog dander that cross-reacts with the major cat allergen, Fel d 1

BACKGROUND: A considerable proportion of animal-allergic patients are sensitized to both cat and dog allergens but knowledge about cross-reactive allergens in cat and dog dander is limited. OBJECTIVE: To investigate whether dog dander contains an allergen that cross-reacts with the major cat allergen, Fel d 1. METHODS: Recombinant Fel d 1 with the same immunological properties as natural Fel d 1 was used for quantitative (CAP) IgE competition experiments performed with sera obtained from cat-allergic patients (n=36). A Fel d 1 cross-reactive dog allergen was characterized by one- and two-dimensional immunoblotting using rFel d 1 for IgE inhibition experiments and with monospecific, polyclonal rabbit anti-recombinant Fel d 1 antibodies. RESULTS: In 25% of Fel d 1-reactive cat-allergic patients, more than 50% inhibition of IgE reactivity to dog allergens was achieved with recombinant Fel d 1. An Fel d 1 cross-reactive 20 kDa allergen with a pI of approximately 3.4 was detected in dander extracts of several different dog breeds. CONCLUSION: This is the first report demonstrating the presence of an Fel d 1-like allergen in dog dander extracts, which may be responsible for double positivity to cat and dog in serology. However, the clinical relevance of this cross-sensitization needs to be confirmed. These results are important for the diagnostic and therapeutic use of dog dander allergen extracts.     

High prevalence of sensitization to cat allergen among Japanese children with asthma, living without cats

BACKGROUND: Cat allergy is common among children with asthma. Many cat-allergic patients in Japan and elsewhere do not keep cats, but nonetheless become sensitized through environmental exposure to cat allergen. OBJECTIVE: To assess the frequency of cat allergy and cat-specific immunoglobulin E (IgE) and immunoglobulin G (IgG) antibody responses in young Japanese patients with asthma in relation to self-reported cat exposure and Fel d 1 levels in dust samples. METHODS: Cat dander-specific IgE antibody was measured in sera from asthma patients using the CAP system. IgE and IgG antibody to Fel d 1 was measured by antigen binding radioimmunoassay and by chimeric enzyme immunoassay. Fel d 1 levels in dust samples from a subset of patients' homes were measured by monoclonal antibody-based enzyme immunoassay. RESULTS: Cat-specific IgE (CAP class>/=2) was found in sera from 70% of 44 patients who kept cats and 34% of 394 patients who had never kept cats. The prevalence of sensitization increased progressively to age 6 years (40%: positive), and then increased gradually to age 16 years (approximately 60%: positive) in patients who had never kept cats. There was an excellent correlation between cat CAP values and IgE levels to Fel d 1. The absolute amount of IgE antibody to Fel d 1 ranged from 0.01 to 15.6% of total IgE. Most patients who did not keep cats were exposed to Fel d 1 levels ranging from 0.07-8 microg/g dust. CONCLUSIONS: Sensitization to cat allergen is common among young asthmatic patients in Japan, even among patients who do not keep cats. Use of CAP and the chimeric enzyme-linked immunosorbent assay allows accurate diagnosis of cat allergy and quantification of specific IgE antibody levels.     

Quantitative measurement of airborne allergens from dust mites, dogs, and cats using an ion-charging device

BACKGROUND: Increasing evidence suggests that children raised with an animal(s) in the house have a decreased risk of becoming sensitized. However, it is not clear whether this phenomenon is related to airborne exposure. OBJECTIVE: To estimate airborne exposure to animal dander and dust mite allergens using a device that can sample large volumes of air silently. METHODS: The device, which uses an ion-charging technique to move air and to collect particles, was run at 1.7 m3/min for 24 h in 44 homes with and without animals. The allergen collected was measured by ELISA for Fel d 1, Can f 1, Der p 1, and Der f 1. RESULTS : Airborne Fel d 1 was present in all homes with a cat (n=27). The quantities measured, i.e. 0.5-20 microg in 24 h, represent 0.01-0.3 microg Fel d 1 inhaled/day at normal breathing rates (20 L/h). Values for houses without a cat were 0.01-0.05 microg inhaled/day. Airborne Fel d 1 correlated significantly with floor Fel d 1 (r=0.58, P<0.001). Results for Can f 1 were similar in houses with a dog, but this allergen was only detected airborne in two houses without a dog. Neither Der p 1 nor Der f 1 (i.e. <0.01 microg) was detected, which represents < or =1 ng inhaled/day during normal domestic activity. During disturbance airborne mite was detected with both the ion-charging device and a filter run in parallel. For cat and mite allergens there was a close correlation between the two techniques (r=0.84, P<0.001). CONCLUSION: Exposure to cat or dog allergen airborne in homes with an animal can be up to 100 times higher than exposure to mite allergen. The results are in keeping with a model where immunological tolerance to animal dander allergens results from high exposure.     

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.     

Allergen avoidance in a day-care center

The predominant sensitizing allergens in Swedish asthmatic children are furred pet animals. Poor ventilation and increased indoor humidity cause accumulation of pet allergens indoors. Indirect contacts with cats also increase pet allergen exposure. We investigated whether the concentration and the total amount of cat (Fel d I) and dog (Can f I) allergen in dust from various surfaces in a day-care center were influenced by extensive renovation, installation of a new ventilation system, ventilation of floors, and avoidance by families and personnel of direct and indirect contacts with pets. The cleaning routine in the day-care center was changed extensively after renovation. Old mattresses, pillowcases, curtains, sofas, and soft toys were removed, and new materials were purchased. Dust was collected from various surfaces before and after renovation from table and chair surfaces, floors, curtains, mattresses, pillows, cushion-like toys, and sofas on five occasions during a 12-month period. Fel d I and Can f I allergen levels were determined by sandwich ELISA. The reduction in the total amount of both Fel d I and Can f I/sampling area was more pronounced than the reduction in the concentration of allergen/g of dust. After renovation, the mean cat and dog allergen concentration was decreased by six and 10 times, respectively. After 1 year, the total amount of cat allergen was lower in all areas (from 24 ng to<1 ng/sampling area, P< 0.05). Already at the first sampling after renovation, the total amount of dog allergen had decreased more than 10 times. In a previous study, we found the median concentration of cat and dog allergen to be 10–30 times higher in ordinary day-care centers. Our present study demonstrates that children changing from a normal center to the renovated center would be exposed to much lower levels of cat and dog allergen. Combined measures such as installation of mechanical ventilation, ventilated floors, regular extensive cleaning, and, probably most important, avoidance of direct and indirect contacts with pets, should decrease cat and dog allergen exposure in day-care centers.     

Influence of cat characteristics on Fel d 1 levels in the home

BACKGROUND: Previous studies investigating cat characteristics and cat allergen production focused on clinical experiments that quantified allergen from either the shaved skin or the fur of the animal; however, these studies did not address these experimental relationships in the home. OBJECTIVE: To determine the relationships between cat characteristics and cat allergen isolated from household dust. METHODS: Fel d 1 allergen levels in dust from homes participating in a population-based study of environmental effect on allergy development were analyzed using a standard monoclonal antibody-based assay. Cat characteristics were based on interviews conducted during home visits by study personnel. RESULTS: Households with any cats had higher geometric mean Fel d 1 levels than households without cats (32.88 vs 0.43; P < .01), and cat allergen levels increased with increasing numbers of cats in the home (P < .01). Length of cat hair, cat sex, reproductive status, and time spent indoors were analyzed; the only characteristic associated with higher levels of Fel d 1 was whether the cat had been neutered or spayed. CONCLUSIONS: Having cats in the home is significantly associated with increased Fel d 1 levels, and having more cats in the home is correlated with more cat allergen. Cat reproductive characteristics may be associated with measurable differences in cat allergen levels.     

Repeated measurements of mite and pet allergen levels in house dust over a time period of 8 years

BACKGROUND: Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time. OBJECTIVE: We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years. METHODS: Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay. RESULTS: Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals. CONCLUSION: Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.     

Etiologic role of unapparent exposure in cat allergy

To determine the importance of unnoticed exposure to cat, we studied 20 patients with a history of respiratory allergy. All the patients had a positive prick test to cat dander extract, and none of them kept cats as pets. The prick test was carried out with a dander extract from cat at a concentration of 100 BU/ml. The specific IgE was determined by the commercially available Pharmacia CAP System. We carried out a conjunctival challenge test. The concentration of Fel d I was quantified in dust samples from the patients' homes by a commercially available method. The patients were reassessed in order to establish a relation between exposure and symptoms, and concealed allergen sources. Sixteen patients, showed significant levels of Fel d I in their homes (mean of 3.35 μg g of dust). The conjunctival challenge test was positive in 15 patients. These patients showed an exposure mean of 0.4 μg/g of dust. The mean levels of specific serum IgE were higher in those patients with a positive challenge than in those with a negative challenge ( P = 0.0145). In nine reassessed patients, a relation was established between natural exposure and the onset of the symptoms. A possible hidden allergen source was established in 11 patients. Hidden exposure to cat allergen may play a role in the symptomatology of many atopic patients, and investigation of sensitization to Fel d I should be included in the routine allergologic evaluation of all patients with asthma or perennial rhinitis.