Food allergens in mattress dust in Norwegian homes - a potentially important source of allergen exposure

BACKGROUND

Sensitization to food allergens and food allergic reactions are mostly caused by ingesting the allergen, but can also occur from exposure via the respiratory tract or the skin. Little is known about exposure to food allergens in the home environment.

OBJECTIVE

The objective of this study was firstly to describe the frequency of detection of allergens from fish, egg, milk, and peanut in mattress dust collected from homes of 13-year-old adolescents and secondly to identify home characteristics associated with the presence of food allergen contamination in dust.

METHODS

Food allergens were measured by dot blot analysis in mattress dust from 143 homes in Oslo, Norway. We analysed associations between home characteristics (collected by parental questionnaires and study technicians) and food allergens by multivariate regression models.

RESULTS

Fish allergen was detected in 46%, peanut in 41%, milk in 39%, and egg allergen in 22% of the mattress dust samples; only three samples contained none of these allergens. All four food allergens were more frequently detected in mattresses in small dwellings (< 100 m(2)) than larger dwellings (≥ 130 m(2)); 63-71% of the small dwellings (n = 24) had milk, peanut, and fish allergens in the samples compared with 33-44% of the larger dwellings (n = 95). Milk, peanut, and egg allergens were more frequently detected in homes with bedroom and kitchen on the same floor as compared with different floors, with odds ratios of 2.5 (95% confidence interval (CI): 1.1, 5.6) for milk, 2.4 (95% CI: 1.0, 6.1) for peanut, and 3.1 (95% CI: 1.3, 7.5) for egg allergens.

CONCLUSIONS AND CLINICAL RELEVANCE

Food allergens occurred frequently in beds in Norwegian homes, with dwelling size and proximity of kitchen and bedroom as the most important determinants. Due to the amount of time children spent in the bedroom, mattress dust may be an important source of exposure to food allergens.

Cat, dog and house dust mite allergen levels on children's soft toys

OBJECTIVE

Children's soft toys are known to harbour house dust mite (HDM) allergens, but little is known whether they harbour cat or dog allergens. The objective of the study was to measure cat (Fel d 1), dog (Can f 1) and HDM allergens on children's soft toys.

METHODS

Dust was collected from 40 children's soft toys and their mattresses. Data were collected on pet ownership. Dust samples were analysed for Fel d 1, Can f 1, Der p 1 and Der f 1 by enzyme-linked immunosorbent assay (ELISA) and results are expressed as median levels with inter-quartile ranges.

RESULTS

Thirty-five (87.5%) soft toys had detectable Fel d 1 levels (median: 0.73 µg/g; inter-quartile range: 0.26-2.56 µg/g) while 34 (85%) had detectable Can f 1 levels (1.20 µg/g; 0.53-2.68). Correspondingly, 32 (80%) mattresses had detectable Fel d 1 levels (0.18 µg/g, 0.07-1.01) while 34 (85%) had detectable Can f 1 levels (0.50 µg/g; 0.33-1.06). All mattresses and soft toys had detectable HDM allergen (Der p 1 + Der f 1) levels with soft toys containing about three times higher levels than mattresses. In homes with cats (n = 10) Fel d 1 levels were higher on soft toys than homes without cats (2.49 versus 0.48 µg/g; p = 0.0009). In homes with dogs (n = 25) Can f 1 levels were generally higher on soft toys (1.38 versus 0.63 µg/g; p = 0.10).

CONCLUSIONS

This study has shown that soft toys can harbour cat and dog allergen as well as HDM allergens, some with very high levels. Cat and dog ownership resulted in higher Fel d 1 and Can f 1 levels on soft toys and mattresses. The levels of Fel d 1, Can f 1 and HDM allergens on soft toys could be of importance to sensitized asthmatic children.

Effect of freezing, hot tumble drying and washing with eucalyptus oil on house dust mites in soft toys

Soft toys are a major source of house dust mites (HDM) and HDM allergens, and sleeping with soft toys is a significant risk factor for HDM sensitization. We studied three techniques to eliminate HDM from soft toys, namely freezing, hot tumble drying and washing with eucalyptus oil. Thirty-six toys (12 in each treatment group) were enumerated for live HDM by the heat escape method before and after freezing overnight, hot tumble drying for 1 h and washing in 0.2% to 0.4% eucalyptus oil. Freezing, hot tumble drying and washing with eucalyptus oil resulted in significant reductions in live HDM, an average reduction of 95.1%, 89.1% and 95.1%, respectively. Additionally, washing with eucalyptus oil resulted in a significant reduction in HDM allergens as well from a geometric mean of 9.12 μg/g to 0.37 μg/g (p = 0.033). These three HDM elimination techniques give parents of infants effective and acceptable methods of limiting HDM exposure.

[House dust mites and their allergens]

The taxonomy, anatomy, life cycle and ecology of Pyroglyphidae mites and storage mites (Acaridae, Glycyphagidae, B. tropicalis) are described. Pyroglyphidae and storage mites have similar morphologies: they are octopods, with characteristic gnathosoma and sensory hairs. Salivary glands and the mid gut produce most of the allergens excreted, which are enzymatic proteins. Biological cycles and development are similar, although fecundity is superior in storage mites compared to the Pyroglyphides. Relative humidity is the main parameter, which regulates mite development, with a higher degree of temperature and humidity required for storage mites. Bedding is the ecological niche of Pyroglyphidae, which feed on human skin. Moulds and food products are the storage mite biotope from which they spread in the dwelling. Initially considered as rural mites, storage mites are also present in urban dwellings. B. tropicalis, in tropical regions is a true domestic mite. Because of this, it is justified to denominate Pyroglyphidae "house dust mites" and storage mites "domestic mites". In addition to the respiratory allergic symptoms, the storage mites can also cause occupational contact dermatoses.

Synergistic effect of multiple indoor allergen sources on atopic symptoms in primary school children

Accumulating data show that the complex modern indoor environment contributes to increasing prevalence of atopic diseases. However, the dose-response relationship between allergic symptoms and complexity of indoor environmental allergen sources (IEAS) has not been clearly evaluated before. Therefore, we designed this study to investigate the overall effect of multiple IEAS on appearance of asthma (AS), allergic rhinitis (AR), and eczema (EC) symptoms in 1472 primary school children. Among various IEAS analyzed, only stuffed toys, cockroaches, and mold patches fit the model of 'more IEAS, higher odds ratio (OR) of association'. The association of IEAS and AR increased stepwise as more IEAS appeared in the environment (1.71, 2.47, to 2.86). In AS and EC, the association was significant only when all three IEAS were present (1.42, 1.98, to 4.11 in AS; 1.40, 1.76, to 2.95 in EC). These results showed that different IEAS had a synergistic effect on their association with atopic symptoms and also suggest that there is a dose-response relationship between kinds of IEAS and risk of appearance of atopic diseases.

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.

Reflections on the control of mites and mite allergens

In cool climates, the humidity circumstances in a home during the summer months are more important for allergen accumulation than those in the winter months. For the same reasons, a reduction of humidity will have a much greater impact during the summer months. Not only the relative humidity, but also the removal of the dust mites' food by cleaning can be an important factor in determining the ultimate level of mite allergens. These theoretic deductions remain to be experimentally tested. An understanding of the dynamics of mite populations and allergen concentrations in homes and public buildings is still hampered by gaps in our knowledge. These gaps mainly concern the food availability and food requirements of dust mites and the kinetics of mite allergens.

Effects of damp and mould in the home on respiratory health: a review of the literature

This review examines whether there is a direct or indirect relation between damp or mould in the home and respiratory health. Home dampness is thought to have health consequences because it has the potential to increase the proliferation of house-dust mites and moulds, both of which are allergenic. The results from the many studies conducted to investigate whether damp and mould are associated with health outcomes are difficult to compare because the methods of measuring exposures and health outcomes have not been standardized. However, the studies that have been conducted in children are probably the most reliable because the confounding effects of active smoking or occupational exposures are absent, and because the presence of symptoms of cough and wheeze have been consistently investigated in many studies. The increased risk of children having these symptoms if the home has damp or mould is fairly small with an odds ratio that is generally in the range 1.5-3.5, these estimates being statistically significant when the sample size has been large enough. This range is consistent with the measured effects of other environmental exposures which are considered important to health, such as environmental tobacco smoke or outdoor air pollutants. The potential benefits of reducing mould in the home have not been investigated, and the few studies that have investigated health improvements as a result of increasing ventilation or reducing damp in order to reduce house-dust mite levels suggest that this intervention is expensive, requires a large commitment, and is unlikely to be successful in the long term. This implies that houses need to be specifically designed for primary prevention of respiratory problems associated with indoor allergen proliferation rather than using post hoc procedures to improve indoor climate and reduce allergen load as a secondary or tertiary preventive strategy.

Domestic mites from an acarologic perspective

Knowledge of the taxonomic, physiologic, biologic, and ecologic characteristics of allergenic domestic mites contributes to the understanding of the causation of many cases of allergic asthma, and to the measures to be taken to control excessive mite occurrence in homes. Domestic mites, i.e., the combined group of storage mites living in the home environment and of pyroglyphid house-dust mites, belong to the subclass of the acari. This comprises also many other mites of medical and economic importance, together with thousands of free-living mites. Because of some species-specific properties of their allergenic products, it is important that the producing mite is always correctly identified. In spite of their small size (approx. 0.5 mm), domestic mites have well-developed and elaborate systems of respiration, digestion, and water balance, enabling them to live and survive in the various habitats of the home environment. Knowledge of the effects of the various and changing ecologic conditions in the home environment is helpful in developing strategies to prevent the establishment and growth of large populations of allergenic domestic mites.