The World Health Organization (WHO) defines CIRS as an acute and chronic, systemic inflammatory response syndrome acquired following exposure to the interior environment of a water-damaged building with resident toxigenic organisms, including, but not limited to fungi, bacteria, actinomycetes and mycobacteria as well as inflammagens such as endotoxins, beta glucans, hemolysins, proteinases, mannans and possibly spirocyclic drimanes; as well as volatile organic compounds.
Many patients don't necessarily "look" sick. But people suffering from CIRS are struggling with an illness that causes them to lose their quality of life, and often times don't know that the cause is a genetic susceptibility to develop this illness based on their immune response genes (HLA-DR). They don't know that the inflammation that makes them ill is due to an assault by their own unregulated innate immune system responses. Because of exposure to mold, they have series of abnormalities in innate immune responses that refuse to self-heal; will not abate in severity - instead, they actually increase; and will continue to cause illness from blood- and tissue-based inflammation as well as alteration of the regulation of fundamental genomic activity.
The WHO further explains that at the core of why one person becomes ill from mold exposure, exhibiting mold sickness symptoms, and another doesn't is simply gene susceptibility (or predisposition). In short, it's what's built into a person's DNA. Every person's immune system is innately personal and genetically coded, meaning that it works differently for each of us. When our bodies are faced with a foreign substance, it immediately begins to process that substance. It recognizes it, determines if it is good or bad, and throws it into the antigen presenting machinery that will normally generate an effective antibody response.