Multiple allergies are perhaps the most obvious sign of immune system overreaction. Patients with CFIDS frequently have a past history of allergies, implying that their immune response is genetically primed for a vigorous response. Other patients with CFIDS develop allergic symptoms after the onset of their illness. CFIDS patients have a hair trigger for allergies.
Allergies can be thought of as an exaggerated reaction of the immune system to harmless allergens, such as pollen and dust. In our model, the overreaction is another sign that in CFIDS the immune system is desperately trying to attack or suppress something. The immune system will react against everything – pollen, dust, foods, odors, chemicals – even if these environmental factors are not causing damage.
(Source: The Doctor’s Guide to Chronic Fatigue Syndrome, by David S. Bell, M.D.)