Multiple chemical sensitivity, MCS

Hornberg C, Wiesmuller GA. Multiple chemical sensitivity, MCS. ALLERGOLOGIE. 2002;25(11):577-584.Immunological alterations are discussed as potential pathomechanisms for multiple chemical sensitivity (MCS) based on the systemic nature of the symptoms, known complex interactions between the immune system and other organ systems, as well as empirical evidence. However, there are theoretical reservations on immunologic mechanisms in MCS and methodological constraints on human trials. Aim of this paper is a critical presentation of immunological concepts of MCS and resulting future research. Clinical manifestations of allergy, pseudoallergy and MCS are discussed as similar, closely related disorders where environmental exposure causes inflammation. In the case of allergy, foreign proteins bind to IgE on mast cells, which release inflammatory mediators. In pseudoallergy, initiating substances directly induce liberation of inflammatory mediators without involvement of antibodies. For MCS, low molecular weight chemicals may bind to chemoreceptors on sensory nerve fibers to release inflammatory mediators. Some proponents of these theories hold that this variable pattern can be attributed to various factors, including "total body burden", "adaptation" and "biochemical individuality". Both "allergic and chemical irritant responses" may be subjected to conditioning, so that the response may be triggered by other stimuli. However, the lack of consistency in response patterns both between and within individual MCS patients limits the plausibility of this hypothesis. Therefore, no consistent pattern of immune dysfunction can be identified in MCS patients. It is recommended that clinical evaluation never be based on results of isolated in vitro assessment of quantity and function of immune system cellular components without considering all variables which apply to all different assays and without knowing the patient's complete history and physical examination