Association of Mold With Asthma Symptoms

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asthmaby Mark T. O'Hollaren, MD

Alternaria alternata is a saprophytic mold typically found in soil and plants, and is considered to be primarily an outdoor allergen. It has been associated with episodes of severe, life-threatening attacks of asthma, and sensitivity to Alternaria (ie, as demonstrated with a positive allergy skin test) has been associated with an approximate 200-fold increase in the risk of a life-threatening asthma attack.[1] Sensitization to Alternaria has also been found to be more common in patients with asthma than in those without asthma.

Salo and colleagues collected data as part of the National Survey of Lead and Allergens in Housing study, and they surveyed a nationally representative sample of over 800 housing units inhabited by over 2400 individuals. They collected dust samples from bed, sofa, or chair, and from the bedroom, living room and kitchen floors, and analyzed for the presence of Alternaria using a polyclonal anti-Alternaria alternata inhibition assay.

They found a positive correlation between the levels of Alternaria in a given indoor environment, and the development of asthma symptoms in those inhabiting that environment. Of interest, they did not find such correlation between this mold and the incidence of allergic rhinitis (hay fever). They concluded that exposure to Alternaria in an indoor environment is associated with active asthma symptoms.

They found a positive correlation between the levels of Alternaria in a given indoor environment, and the development of asthma symptoms in those inhabiting that environment. Of interest, they did not find such correlation between this mold and the incidence of allergic rhinitis (hay fever). They concluded that exposure to Alternaria in an indoor environment is associated with active asthma symptoms.

Viewpoint

This is an important study for several reasons. First, it builds on the increasing evidence that all allergens are not created equal. Namely, that some (eg, pollens) are more likely to cause symptoms in the upper airway (ie, allergic rhinitis), and some (such as Alternaria) are more likely to cause symptoms in the lower airway (ie, asthma). Thus, allergy to Alternaria is more likely to cause asthma symptoms than symptoms of allergic rhinitis. The latter has also been suggested by Gergen and Turkeltaub.[2] Second, the study demonstrates that Alternaria is an important indoor allergen. Given this allergen's reputation as a potent asthma trigger, we now need to be aware that indoor exposure is also important for patients with asthma.

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