Current indoor allergen levels of fungi and cats, but not house dust mites, influence allergy and asthma in adults with high dust mite exposure

17. Dharmage S, Bailey M, Raven J, Mitakakis T, Cheng A, Guest D, Rolland J, Forbes A, Thien F, Abramson M, Walters EH. . American Journal of Respiratory and Critical Care Medicine. July, 2001; 164(1):65-71.

Purpose: The authors investigated the influence of indoor levels of fungi, dust, and cat allergen on sensitization and asthma in adults.

Design: Two-phase sampling from European Community Respiratory Health Survey ("ECRHS") cohort study. Data were collected using questionnaires, skin prick tests, and lung function tests. Bedroom dust and air samples were analyzed for dust mite allergen, cat allergen, and fungal colony forming units ("CFU") per cubic meter of air. Fungi also were assessed indirectly using ergosterol levels. Controls consisted of survey participants that did not have current asthma, bronchial hyper-reactivity, or wheezing.

Outcome: A total of 485 subjects responded to the questionnaire and had clinical tests conducted. Three quarters of the subjects were exposed to allergen levels higher than the levels proposed by the American Academy of Allergy, Asthma and Immunology. They also found high levels of fungi in the air of half the homes studied. High levels of total airborne fungi were actually associated with decreased sensitization to fungi. On the other hand, the risk of bronchial hyperactivity was significantly greater in subjects with high total fungal levels compared to the group with the lowest fungal levels. Higher levels of cat allergen exposure led to increased clinical activity of asthma and sensitization in young adults; however, high levels of house dust mite allergen levels seemed to have no direct correlation with the presence of asthmatic symptoms.

Significant Quotes:
"High Fel d [cat allergen] 1 levels in floor dust were found to increase the risk of current asthma. Although Der p [house dust mite allergen] 1 levels in homes were high, people exposed to high Der p 1 levels in floor dust were less likely to be sensitized to house dust mites or to have wheezed within the past year." (p. 65).

"Our findings on the influence of ergosterol on sensitization to fungi and clinical activity of asthma are novel." (p. 71).

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