Cladosporium Spores May Protect Against Allergies in Children

CINCINNATI, June 16 - When it comes to inducing allergies in young children, not all types of airborne fungal spores are created equal, researchers here have found.

Some types of fungi, such as Apergillus, appear to sensitize children to a wide variety of allergens, while another type, Cladosporium, seemed to protect against allergic sensitization, said Tiina Reponen, Ph.D., of the University of Cincinnati.

In some children, exposure to Cladosporium spores was associated with a 40% reduction in the odds for testing positive to any allergen on a skin prick test, Dr. Reponen and colleagues said online in Pediatric Allergy and Immunology.

The researchers collected fungal spores from the homes of 144 infants enrolled in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS) during 2003 and 2004. Children in this study had at least one parent with a positive skin prick test. The researchers identified and counted the spores via microscopy. The children, all between the ages of one and three, received a clinical exam and a skin prick test for 17 allergens.

Analysis of the relationship between fungi types found in the home and rhinitis symptoms or a positive skin prick test in the children yielded the following results:

• Basidiospores were significantly associated with rhinitis symptoms, regardless of skin prick test results (odds ratio not given; P<.01).
• Ganoderma was also associated with rhinitis symptoms, although the trend was not statistically significant (OR not given; P<.10).
• Penecillium, Aspergillus, and Alternaria spores were significantly associated with a positive skin prick test for any allergen (ORs not given; P<.01 for all).
• Cladosporium, however, was inversely associated with a positive skin prick test for any allergen (OR not given; P<.05). Further analysis showed that if the mother was sensitized to Cladosporium, exposure to this fungus reduced the odds of a positive skin prick test for any allergen in her children (OR=0.6; 95% CI=0.4 to 0.9).

That last finding was surprising, especially since Cladosporium has been linked to allergic sensitization in adults, the researchers said. However, this fungus could have an entirely different effect on a child's developing immune system, they added. Cladosporium exposure might inhibit a developing immune system's Th2 cell response, thereby decreasing the likelihood of allergic reactions, they speculated.

"To our knowledge, this study is the first one to report an inverse association between fungal exposure and health outcome (rhinitis and allergic sensitization) in infants," the researchers said.

The study found no association between total concentration of fungal spores in the home and rhinitis or positive skin prick test.

"We believe that contrasting relationships among the various fungal genera to the health outcomes investigated in this study might actually cancel the effect that total concentration may have on these outcomes," the researchers said. "This finding would help to explain some of the lack of association in the reporting of health effects and total fungal spore concentrations observed in previous studies."

However, the indoor environment is a complicated one where allergens, pollutants, and toxins mix and have the potential for synergistic relationships, which were not examined in the current study, the investigators noted.

"Based on the data presented in this paper, it appears that clinicians and researchers should be attentive to the composition of the fungal spore profile and the respective concentrations of the fungal genera present rather than total or culturable spore count alone," the researchers concluded.

They pointed out that as the study was conducted in an infant population the health outcomes may or may not be transient.

"Long-term follow-up of this cohort will show how early fungal exposure affects the development of allergy and asthma in children later in life," they wrote.