1014 Mites, cockroaches and allergic rhinitis

While the implications of the ‘hygiene hypothesis’ might persuade many parents to be less fastidious about absolute cleanliness and allow their children to live less-protected lives, the situation gets to be quite challenging when one learns who the cohabiters of the home environment might be. In a recent article from the ENT Clinic at the Free States’ Universitas Hospital, researchers reviewed the results of skin prick and RAST tests in 50 patients attending for management of moderate to severe allergic rhinitis. The test battery included sensitivity to usual grass species, dog and cat epithelia, feathers, house dust mites, storage mites, spider mites and cockroaches. House dust mites favour humid conditions and do not survive dehydration. Storage mites favour stored food as their preferred habitat and also require humid conditions (80% relative humidity). Spider mites are found outdoors and have been found to be important allergens in agricultural workers. These mites thrive in conditions of low humidity. Cockroach allergens are derived from their saliva, faeces, secretions, cast skins, debris and dead bodies. The Free State study population ranged in age from 5.6 and 57.2 years and most (82%) lived in an urban environment. Grass pollens were the most common allergens with around 60% of patients reacting to the tests. House dust mite sensitization was found in 46% but was more prevalent in patients who had previously lived at the coast. Storage mites were not common allergens in this group but reactions to the spider mite were found in 46% (with fair to good agreement between sensitisation to this mite and the house dust mite. Thirty-eight percent of subjects showed sensitivity to the cockroach species B germanica. IgE levels were not universally raised, with 8% of patients having normal levels. The point is made that this epidemiological study is relevant for this particular part of the country, and different prevalence figures have been shown for other areas in other studies.

Read more:
Curr Opin Pulm Med 2005; 11: 14-20
S Afr Med J 2010; 100: 160-3
Curr Allerg Asthma Rep 2005; 5: 411-6