House dust mite | Cockroach | Mold
Cockroach-specific IgE antibodies are frequently found in patients with asthma and other allergic conditions all over the world. The most important species in industrialised countries are the German and the American cockroaches.
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 sensitisation.
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.
Cockroach may commonly induce symptoms of asthma, allergic rhinitis, allergic conjunctivitis and allergic eczema in sensitised 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, sensitisation is usually to multiple indoor and/or outdoor allergens.
Alternaria alternata /Alternaria tenuis
Alternaria alternata is one of the most important among the allergenic moulds. 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.
Alternaria occurs on many plants and other substrates, including foodstuffs and textiles. Favourite 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 mould spores found in dwelling dust in both North America and Europe.
Alternaria is predominantly an outdoor allergen favouring 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.
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 mould and has been shown to exhibit high cross-reactivity to other fungal enolases.
Sensitivity to Alternaria has been increasingly recognised 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-sensitised patients may also be at risk for allergic rhinitis. Severe cases of rhinitis may be attributable to Alternaria sensitivity.
Alternaria sensitisation 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.