Negative Mold Allergy Tests

Despite having significant visible mold growth in the walls of our house and high levels of Aspergillus and Penicillium airborne mold levels and allergy-type respiratory health problems, my mold allergy tests came out negative.  Does this mean that I am not allergic to mold and that mold is not likely to be a cause of my respiratory problems (even though I get better when I am away from our house)?-Anon

 

            One certainly could interpret it that way and many physicians (including allergists) would.  That would be the case if the limitations of allergy testing were not taken into consideration.  Most allergy testing is conducted by injecting a prepared allergen mix under the skin and then following up to determine the size (if any) of the wheal produced in response to the allergen (allergens). 

            With allergens such as dust mite, cat, dog, cockroach, allergen preparations are relatively pure and specific.  As such, one can be reasonably certain that on testing one is for the most part either allergic or non-allergic to the tested allergen. 

            Testing for allergic responses for mold is far less definitive.  There are well over 60 mold types in both the indoor and outdoor environments that can cause allergic reactions in humans.  Allergen preparations used in allergen testing typically consist of 6 mold types in three mold mixtures.  These are characterized to genus and not to species.   

When one is tested for sensitivity to Penicillium, there is no science that indicates that the allergic response will be the same for the 10 or so different species of Penicillium that one could be exposed to in building or outdoor environments.  This would also be true for the 10 or so species of Aspergillus.  Unfortunately the science of determining the cross-reactivity of species in these two important fungal genera has yet to be done.  As such, a negative test result to an allergen test mixture that contains Aspergillus or Penicillium cannot be used to eliminate the possibility that exposures to elevated levels of airborne mold spores of specific species of these two genera is the cause of allergy-type symptoms that you  have been experiencing in your house.

 February 19, 2007