Dr. Nicolson said he would approach the problem of MCS from a biological direction. His involvement with Gulf War illness began when his daughter (who was serving there) experienced symptoms, but could find no help for them. She became unable to continue with pilot training in the Army and changed careers to medicine. In the process of trying to help her, Dr. Nicolson became involved in a large project on the diagnosis of chronic infections in a variety of fatiguing and autoimmune illnesses, including GWI.

Chronic infections by themselves can create illness, but they seem to act in conjunction with other factors, such as chemical and environmental exposures. Multiple biologic exposures also play a role in creating chronic illness. So does genetic predisposition, but little is known about this. Dr. Nicolson hypothesizes that a variety of bacterial and viral infections play an important role as causative agents, cofactors, or opportunistic infections. Together they provide an important source of morbidity in patients with a chronic illness. These infections are often opportunistic, as patients with chronic illness resulting from environmental or chemical exposures are more susceptible to them. He said that he did not intend to argue whether or not they are the sole cause.

Dr. Nicolson and his colleagues conducted a study of the signs and symptoms of 650 Gulf War veterans beginning in the early 1990s, before the media frenzy about GWS began. Dr. Nicholson commented that the label "Gulf War syndrome" presumed that medicine knew more than it did about the illnesses associated with the Gulf War. A survey form was distributed to veterans of the Gulf War, asking about signs and symptoms before, during, and after the war; where they served; what previous diagnoses they had had; their illness state; their environmental exposures; their vaccination record; what treatment they had had; and the condition of their family members. At the same time, a U.S. Senate survey was studying 1,200 families of Gulf War veterans, as there were indications that symptoms were spreading to family members. In this study, approximately 77% of spouses and 65% of children born after the war showed similar signs and symptoms to patients with GWI.

In the Gulf War there was a variety of potential toxic exposures: chemicals, radiologic exposures (and not just to depleted uranium); environmental exposures like sand and smoke; and biological exposures.

Many of the signs and symptoms of biological exposures are not easily separated from those of chemical exposures. The biological exposures are of particular interest because of the spread of illness to families. Nicolson and his colleagues focused on mycoplasma species, theorizing that these could lead to family members becoming sick. Family members would not likely become sick through handling the veterans= equipment, or if the illness was due to PTSD. The estimate is that at least 40% of GWI may be due to specific biological exposures such as mycoplasmal infections; so mycoplasmal infections do not explain everything, but could be a subset that causes illness to spread to families. Sixty families were studied. Most, but not all, the children were symptomatic and showed similar signs and symptoms as the family member who was a veteran. When the illness was passed to families there was a high incidence of similar infection found in every symptomatic family member.