Multiple chemical sensitivity syndrome
Multiple Chemical Sensitivity Syndrome (MCS) is characterized by an increasing intolerance to common environmental chemicals at levels that do not typically affect most individuals. This condition can manifest after exposure to various substances, such as solvents, pesticides, and other chemical agents found in everyday environments, which may lead to symptoms affecting multiple body systems, including the nervous, immune, and respiratory systems.
Individuals with MCS often experience a range of symptoms, including headaches, chronic fatigue, respiratory issues, and musculoskeletal pain. The severity and frequency of these symptoms can fluctuate with exposure to offending substances. Diagnosis typically requires meeting specific criteria, including symptom recurrence upon exposure and symptom improvement after removing the trigger.
Although the exact prevalence of MCS is uncertain, the condition is recognized in association with overlapping disorders like sick building syndrome and reactive airway disease. Treatment generally focuses on alleviating symptoms and providing supportive care, as no definitive cure exists. Research continues into the mechanisms underlying MCS, including potential neurogenic inflammation and immune responses, but a consistent physiological abnormality has yet to be identified. Understanding and addressing MCS remains a complex challenge, often requiring a multidisciplinary approach.
Multiple chemical sensitivity syndrome
ANATOMY OR SYSTEM AFFECTED: Eyes, immune system, lungs, muscles, nerves, nervous system, respiratory system, skin
DEFINITION: An increasing intolerance to commonly encountered chemicals at concentrations well tolerated by other people
CAUSES: Environmental exposure to chemicals
SYMPTOMS: Headaches (often migraine), chronic fatigue, musculoskeletal aching, chronic respiratory inflammation (rhinitis, sinusitis, laryngitis, asthma), attention-deficit disorder, hyperactivity (affecting younger children), food intolerance
DURATION: Acute to chronic
TREATMENTS: Alleviation of symptoms, supportive therapy
Causes and Symptoms
Multiple chemical (MCS) syndrome, environmental intolerance (IEI), reactive airway disease, and sick building syndrome are overlapping disorders caused by intolerance of environmental chemicals. Exactly how many people are affected by MCS is unknown. The onset is often associated with initial acute chemical exposure; patients may report the onset of MCS after moving into a new house, being exposed to chemicals in the workplace, or using pesticides in the home. Patients often describe an increasing intolerance to commonly encountered chemicals at concentrations well tolerated by other people. Diagnosis is made when the following six criteria are met: repeated exposure reproduces symptoms, the condition is chronic, low chemical exposure levels cause symptoms, symptoms improve with the removal of offending chemicals, responses are triggered by multiple unrelated chemicals, and multiple systems are affected.
Symptoms usually wax and wane with exposure and are more likely to occur in patients with preexisting histories of migraine or classical allergies. Idiosyncratic medication reactions (especially to preservative chemicals) are common in MCS patients, as are dysautonomic symptoms (such as instability), poor temperature regulation, and food intolerance. It is thought that patients with MCS have organ abnormalities involving the liver, the (including the and the limbic, peripheral, and autonomic systems), the immune system, and perhaps porphyrin metabolism, probably reflecting chemical injury to these systems. There is often a substantial overlap of MCS symptoms with and chronic syndrome.
The common clinical symptoms may include (often migraine), chronic fatigue, aching, chronic respiratory (rhinitis, sinusitis, laryngitis, asthma), attention-deficit disorder, and hyperactivity in younger children. Less common complaints include tremor, seizure, and prolapse. Agents associated with the onset of MCS include gasoline, kerosene, natural gas, pesticides (especially chlordane and chlorpyrifos), solvents, new carpet and other renovation materials, adhesives and glues, fiberglass, carbonless copy paper, fabric softener, formaldehyde and glutaraldehyde, carpet shampoo (lauryl sulfate) and other cleaning agents, isocyanates, combustion products (poorly vented gas heaters, overheated batteries), and medications (dinitrochlorobenzene for warts, intranasally packed neosynephrine, prolonged antibiotics, and general with petrochemicals).
It is believed that the mechanisms that lead to MCS may be multifactorial and include neurogenic inflammation (respiratory, gastrointestinal, and genitourinary symptoms), kindling and time-dependent sensitization (neurologic symptoms), and immune activation or impaired porphyrin (multiple-organ symptoms). Pathological findings of MCS have rarely been examined. A preliminary study of nasal in these patients indicates that they are characterized by defects in the junctions between cells, desquamation of the respiratory epithelium, glandular hyperplasia, lymphocytic infiltrates, and peripheral nerve fiber proliferation. A consistent physiologic abnormality in these patients has not been established.
Psychiatric, personality, cognitive/neurologic, immunologic, and olfactory studies have been conducted comparing MCS subjects with various control groups. Thus far, the most consistent finding is that patients with MCS have a higher rate of psychiatric disorders across studies and relative to diverse comparison groups. Since these studies are cross-sectional, however, causality cannot be implied. Various working groups have proposed several research questions addressing the relationship between neurogenic inflammation and toxicant-induced loss of tolerance with the development of MCS.
Treatment and Therapy
The management of patients with MCS at present involves symptomatic and supportive therapy. There is a general consensus among researchers and clinicians that in order to treat patients with MCS effectively, a double-blind, placebo-controlled study performed in an environmentally controlled facility, with rigorous documentation of both objective and subjective responses, is needed to help elucidate the nature and origin of MCS.
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