Environmental challenges for patients with nuisance symptoms, chronic cough, and asthma are difficult to establish cause and effect relationships because there is often no objective measurements to confirm clinical changes. Inflammatory markers are usually not abnormal in this group and spirometry is not as reliable as with the interstitial lung diseases.

Mechanisms of these symptoms may be allergic or irritant type and require only a short time period of avoidance (3-5 days) of the causative environment for symptoms to return to a baseline level in those with pre-existing symptoms, or resolve completely in those without pre-existing symptoms. Patients in whom the disorder is mediated through an inflammatory mechanism require a longer period out of the environment for symptoms and signs to change.

Challenges are more difficult to clearly define a causal relationship between an environment and the symptoms expressed by the patient when a pre-existing disorder is present compared to those patients who had no pre-existing symptoms.

Situation 1: A patient with perennial allergic rhinitis and mild asthma feels that something in the home has worsened baseline nasal and chest symptoms within the past 6 months based upon observation of improvement on a 5 day trip and recurrence upon return to the home. Skin testing revealed negative responses to dog and positive responses to mold and dust mites. An environmental history reveals a slight "musty" odor in the home. A dog was acquired one year ago and is known to "mark territory" over a carpeted area. There had been an air conditioning condensate line blockage causing overflow of the condensate pan on two occasions in the past two years leading to significant dampness in the carpet around the air conditioning system. No other family member seems affected.

The pattern that suggests a home contamination is playing a role is an increased frequency and/or intensity of symptoms than have previously been experienced and the improvement upon a short time away from the home. The environmental history gives clues to suggest that a contamination is present. Confirmation of a contamination, however, does not establish cause and effect.

Patients who have not experienced pre-existing symptoms would be expected to become asymptomatic within a defined time period after being removed from a contamination.

Patients with pre-existing symptoms would be expected to return to levels of symptoms and medication use that was typical prior to the contamination.

If one can establish such a pattern of reactivity as described above, this is enough to recommend a survey of the home, attempting to determine a source of a contamination.

Effective remediation of a contamination should lead to resolution of symptoms in the patient without pre-existing problems and return to baseline for those that have a long-term history.