The most common complaints–fatigue, headache, nausea, malaise, pain, mucosal irritation, disorientation, and dizziness–are nonspecific. All these symptoms can occur in diseases with specified pathologic characteristics, but they also occur commonly in the absence of physical illness.
No gross or microscopic evidence of inflammation or other objective signs of a disorder have been associated with IEI.
The list of the specific items believed to cause this condition is virtually unlimited. It includes any naturally occurring food, including drinking water; artificial food additives of all types; almost any synthetic product; specific chemicals such as formaldehyde, phenol, ethanol, ammonia, “hydrocarbons,” and “petrochemicals”; and sources of environmental chemicals, particularly cleaning solvents, paints, smoke, gasoline, vehicle exhaust fumes, fumes from office machines, perfumes, synthetic clothing, pesticides, structural plastics, building construction materials, and new carpeting. In many cases, patients complain of difficulty in stores, shopping malls, and public buildings. Although the emphasis is on synthetic chemicals, causes of illness have also included natural gas, electromagnetic radiation, viruses, fungi, yeast, and wood dust. In certain cases, the causative chemical is an endogenous hormone, especially progesterone. Patients with the diagnosis of environmental illness almost always attribute their illness to many of these substances and usually to a combination of foods, environmental chemicals, and drugs.
The items listed here as “causes” are believed to act in a dual role, both in the induction of the disease and in provoking symptoms once disease occurs. A unique feature of environmental illness is the absence of a consistent dose-response relationship in provocation of symptoms. The length of exposure to environmental agents required to induce the disease has varied from seconds to years with no correlation of presumed dose and length of exposure to the severity of illness.
The diagnostic procedure most commonly used by clinical ecologists is provocation-neutralization, discussed later in this chapter. After provocation-neutralization testing, many of these patients develop a new list of “causes” corresponding to the items used in the test.