House dust mite | Cockroach | Mold

  d1 House dust mite

Allergen description

Dermatophagoides pteronyssinus

Family:

Pyroglyphidae

House dust mites are one of the most common sources of sensitization in all parts of the world. Dermatophagoides pteronyssinus, D. farinae and D. microceras occur in the same areas, but the relative proportions of their distribution vary geographically.

Mites have a life cycle of about 2 to 3 months. The size of the mite is up to 0.3 mm. They live in house dust and thrive in warmth and high humidity. Mites’ faeces seem to be the major source of allergenic exposure. They are about the size of a pollen grain and can therefore very easily become airborne and penetrate the lung alveolus.

Allergen exposure

Dust, carpets, pillows, mattresses and upholstering furniture containing biological material, especially human dander, are reservoirs of house dust mites. Other sources of exposure are damp houses (>45% relative humidity) or dwellings at low altitudes.

Cross-reactivity

Allergens from mites have both common and speciesspecific determinants. Allergenic determinants are shared with other mites belonging to the Pyroglyphidae family and are highly cross-reactive with other Dermatophagoides species. There seems to be a limited cross-reactivity with storage mites (nonpyroglyphid). Some mite allergenic proteins such as tropomyosin are widely cross-reactive among invertebrates such as shrimps, snails, cockroaches and chironomids.

Clinical experience

IgE-mediated reactions

Studies of house dust allergic individuals around the world have shown that house dust mites are one of the most common causes of symptoms such as perennial type asthma, rhinitis and conjunctivitis, often with nocturnal or early morning episodes.

There is evidence that reduction of mite-allergen levels can cause a major improvement in symptoms of asthma. So far the only effective way to get a permanent reduction of house-dust mite allergens seems to be lowering of the air humidity and temperature together with efficient cleaning.

  i6 Cockroach

Allergen description

Blatella germanica

Cockroach-specific IgE antibodies are frequently found in patients with asthma and other allergic conditions all over the world. The most important species in industrialized countries are the German and the American cockroaches.

Allergen exposure

The distribution of cockroaches in the world varies with geography, climate and culture. Cockroaches thrive in damp and warm environments. They are rarely found in dry, high altitude areas.

Several species are widespread and still expanding in new areas. The most common of these is the German cockroach. It is a small cockroach, growing up to approx. 2 cm in length that is found throughout the world in association with humans. Adults have wings, but rarely fly. The nymphs are darker and wingless.

Cockroaches are found in homes, restaurants, hotels, food plants, warehouses, etc. During the day, the roaches may cluster hidden behind baseboard molding, in cracks around cabinets, closets or pantries and in and under stoves, refrigerators and dishwashers.

Cockroaches produce potent allergens. At least 29 allergens have been detected from German cockroach contributing to asthma.

Allergic individuals can be exposed to cockroach allergens by inhalation from living quarters and by ingestion due to contamination of foodstuffs. The highest levels of cockroach allergens are typically found in the kitchen. However, the lower levels of allergen found in bedding, on the bedroom floor and in sofa dust may be more relevant in causing sensitization.

Cross-reactivity

An extensive cross-reactivity among different species of the genus has been demonstrated. Extensive cross-reactivity has also been demonstrated between tropomyosin found in shrimp and that in other Crustacean species, house dust mite and German cockroach.

Clinical experience

IgE-mediated reactions

Cockroach may commonly induce symptoms of asthma, allergic rhinitis, allergic conjunctivitis and allergic eczema in sensitized individuals.

The clinical presentation of asthmatic patients with cockroach allergy is typically nonspecific. Most commonly, patients have a history of perennial asthma, possibly worse in the winter, without a clear history of onset of symptoms on exposure to cockroaches.

Although some patients may be exclusively allergic to cockroaches, sensitization is usually to multiple indoor and/or outdoor allergens.

  m6 Mold

Allergen description

Alternaria alternata /Alternaria tenuis

Alternaria alternata is one of the most important among the allergenic molds. Although other Alternaria species are probably also clinically relevant, especially as a result of cross-reactivity between the species, most research has been directed toward Alternaria alternata.

Allergen exposure

Alternaria occurs on many plants and other substrates, including foodstuffs and textiles. Favorite habitats are soils, corn silage, rotten wood, compost, bird nests, and various forest plants. Black spots on tomatoes may be caused by Alternaria. It is frequently found on water condensed on window frames. It is one of the most common mold spores found in dwelling dust in both North America and Europe.

Alternaria is predominantly an outdoor allergen favoring damp spots, and most indoor concentrations may derive from outdoor primary sources.

In temperate climates, airborne Alternaria spores are detectable from May to November, with peaks in late summer and autumn. Despite the large spore size, spores may disperse for hundreds of miles from the source.

Cross-reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected. Enolase is a common allergen found in many species of mold and has been shown to exhibit high cross-reactivity to other fungal enolases.

Clinical experience

IgE-mediated reactions

Sensitivity to Alternaria has been increasingly recognized as a risk factor for the development, persistence and exacerbation of asthma. Studies have suggested that sensitivity to Alternaria may be a risk factor for life-threatening asthma. Alternaria is one of the main allergens affecting children.

Alternaria-sensitized patients may also be at risk for allergic rhinitis. Severe cases of rhinitis may be attributable to Alternaria sensitivity.

Alternaria sensitization may also occur in occupational settings, including gardens, bakeries, forests and farms.

Alternaria is associated with baker’s asthma and wood pulp worker’s lung.