Sensitivities to chemicals and odors are considered to be in a separate class from true allergies because they are not mediated by the same immunologic mechanisms. There is considerable discussion as to what actually causes chemical sensitivities, but most researchers agree that they also involve immune system activation. Patients with chemical sensitivities as their most debilitating symptoms are said to have environmental allergy or chemical sensitivity syndrome. However, these symptoms are frequently seen in CFIDS, usually in a mild form, and the symptoms are elicited only by direct questioning. It is my feeling that in patients with severe chemical sensitivities who also have the symptoms of exhaustion, joint and muscle pain, headache, sore throat, and abdominal discomfort, CFIDS probably is the casue of the chemical sensitivities.
(Source: The Doctor’s Guide to Chronic Fatigue Syndrome, by David S. Bell, M.D.)