It has been difficult to confirm that a given building is responsible for allergic symptomatology, exacerbation of asthma, or immunological dysfunction. In fact, in most studies, few objective immunological parameters have been studied and only rarely has there been any quantitation of IgE or secondary mediators. Furthermore, although many studies deal with rhinitis or respiratory tract irritation, there is a misconception that all such symptoms are allergic in nature, and studies attempting to prove that allergies are caused by buildings frequently neglect to prove that these are indeed true allergic responses. In addition, many of the symptoms that people attribute to sick building syndrome (SBS) or building-related illness, such as headaches, dizziness, fatigue, nausea, cough, and eye irritation, are subjective, and studies often fail to take into account other possible causes that may be inherent in the subjects, such as sinusitis, hyperventilation syndrome, or psychosomatic illness. Unfortunately, most clinical studies on SBS pay little attention to the preexisting conditions that a subject may have and discount the possibility that the inciting agent does not cause symptoms, but merely exacerbates a preexisting condition. Moreover, they offer no information about the nature of the mechanisms of action or pathophysiological relationships. Clearly, further studies are necessary to further explain the complexity of complaints that currently exist. Indeed, SBS might properly be paraphrased as "what is it?--if it is!"