When travelling this week, I was reading the latest Indoor Air journal and there were two interesting articles that both studied the relationship between mold and dust mites.

The first article was titled, A comparison of the allergic responses induced by Penicillium chrysogenum and house dust mite extracts in a mouse model _¹.  Lab mice were exposed to varying concentrations of extracts from house dust mites and the mold Penicillium chrysogenum.  Here is a quote from the article,

“Our data suggest that Penicillium chrysogenum is a robust allergen and may be a more potent allergen source than house dust mite in this mouse model…   P. chrysogenum as well as other molds may play an important role in asthma development in our society.”

Although the article doesn’t address setting acceptable exposure levels for humans, the article shows the dose response figures for mice based on several health outcomes.

The second article I read that addressed mold and dust mites was A dose-dependent relationship between the severity of visible mold growth and IgE levels of pre-school-aged resident children in Taiwan _².  I found this to be a fascinating article that wonderfully illustrates the point that it’s not exclusively mold that causes health effects in damp environments.

The study found a statistically significant dose-dependent relationship between severity of indoor visible mold growth and total serum antibody (IgE) levels.  So far, so good.  But when they looked at the specific type of antibodies (as opposed to the total), they didn’t find a correlation with fungal allergens.  They did however, find that dust mite antibodies corresponded with the indoor visible mold growth.

So what was going on?  The authors suspect that the degree of visible mold growth is an indicator of dampness.  The mold itself may not be affecting the children’s health, but the dampness leads to elevated concentrations of other exposures, such as dust mite colonies, that do affect health.  They recommend that studies done on the health effects of mold should control for these other exposures.

So to sum up, the first study found that a common type of mold was a more potent allergen than dust mites.  The second study found dust mites to be causing greater allergic responses than mold.  How can we explain the difference in these conclusions?

1. The first study was done on mice, the second on children.  Mice are different than children (one notable difference… my children are much LOUDER than mice!)

2. The first study exposed mice to equal amounts of Penicillium chrysogenum allergen and dust mite allergen.  But in a typical home, are there really an equal amount?  We can say that Penicillium chrysogenum is more potent gram for gram, but exposure to dust mite allergen may be several orders of magnitude greater.

3. In the second study, although total IgE antibodies were more closely correlated to dust mites, they could not establish solid statistical significance.  Also, they didn’t control for many other common indoor allergens like cockroach, which can be found in damp indoor environments.

Do these studies have anything in common?  Yes! They share the conviction that exposures to contaminants found in damp buildings can illicit a measurable affect on health.  That is a powerful message.

1. Ward, M. D. W., Chung, Y. J., Copeland, L. B. and Doerfler, D. L. (2010), A comparison of the allergic responses induced by Penicillium chrysogenum and house dust mite extracts in a mouse model. Indoor Air, 20: 380–391. doi: 10.1111/j.1600-0668.2010.00660.x
2. Hsu, N.-Y., Wang, J.-Y. and Su, H.-J. (2010), A dose-dependent relationship between the severity of visible mold growth and IgE levels of pre-school-aged resident children in Taiwan. Indoor Air, 20: 392–398. doi: 10.1111/j.1600-0668.2010.00663.x