Carlos Fernando Collares 1 & Paulo Cesar Trevisol-Bittencourt 2

1.Sao Paulo Poison Control Center. 2. Federal University of Santa Catarina

Chemical intolerance (CI), which is also known as multiple chemical sensitivity (MCS) or idiopathic environmental intolerance (IEI), among other names, is still a poorly understood condition in Brazil. Occupational and environmental exposures leading to odor intolerance and other symptoms are quite common in this country, but most of them are not reported.

     It is interesting to notice that developed countries largely attribute the CI phenomenon to “mass hysteria” generated by media sensationalism. However, in Brazil, where there is no media-attributable bias, workers exposed to volatile organic compounds may present intolerance to odors after extremely low-level chemical exposures, including compounds molecularly unrelated to the ones implicated to be symptom-triggering during initial stages of the illness.

     As a matter of fact, CI has rarely appears in Brazilian judicial litigations. When it does, it is described with other names, such as “cross-reactive allergy“. There is also a dispute here for the correct denominations trying to describe different CI situations, probably due to its still controversial physiopathology and the ongoing debate about its existence as a distinct nosological entity (Staudenmeyer et al., 2003). Currently, most of Brazilian cases are simply diagnosed as a psychiatric disease, mostly somatoform or anxiety disorders – which are, in fact, commonly presented by CI patients.

     Toxicology education for Brazilian primary care physicians and specialists is almost inexistent, analytical resources are scarce and Brazilian public health system is very problematic. This situation causes a serious difficulty in the establishment of any causal nexus between exposure and symptoms. Many Brazilians with CI then initiate an exhausting journey through different medical specialists, which are mostly incapable of putting an end to their suffering, since the numerous requested exams are usually negative.

     Nevertheless, Brazilian judicial decisions have already accepted these “allergies” as occupational disorders, granting compensation and other benefits to a still small number of workers. Nowadays, the vast majority of health-related litigations due to occupational chemical exposures are favorable to employers.



     Despite the recent scientific acceptance about the occurrence of neurobiological phenomena in CI patients, the dispute about distinguishing psychiatric and toxicological etiological factors remains a critical issue. This is particularly relevant when it is considered the significant overlap between the diagnosis of MCS and other “functional” or “medically unexplained” illnesses, such as chronic fatigue syndrome, fibromyalgia and irritable bowel syndrome (Aaron & Buchwald, 2001).

     Sternberg (2001), inspired by the Ancient Greek society and their divinities, described the biology of neuroimmunomodulation in health and disease and the important role of emotions and the environment in these processes. She states that a reconceptualization of mind-body relationships is now possible after the considerable growth in the number and quality of research papers. It is now widely recognized that not only “medical” conditions may initiate with psychiatric manifestations but also that stressful events may actually worsen “organic” diseases. Under a toxicological perspective, Vogel (1993) had already stated that stress may alter results of toxicity tests.

     Furthermore, current neuroimmunotoxicology studies are contributing to unveil the pathophysiology of various diseases as well as new diagnostic and therapeutic procedures to be used in patients with neurotoxic exposure. Sullivan al. (2001) pertinently ask: are psychiatric conditions a cause, an effect, a predisposing factor or a comorbidity to MCS?

Despite the alleged lack of consistent, credible immunotoxic alterations associated to CI / MCS, an intriguing article from Rowat (1999) collects hundreds of references to propose the concept of integrated defense systems, which would involve neuroendocrine-immune pathologic interactions. These systems would include e.g. neural sensitization, limbic kindling, neurogenic switching and also traumatic dissociation. Particularly regarding CI, he proposes that these mechanisms could be directly triggered by certain commonly implicated chemicals. Among the innumerous other hypotheses, heme biosynthesis disorders have also been implied as a major causative factor (Ziem, 1997), as well as NMDA activation and sensitization (Pall, 2003).

     Public awareness to Environmental Health has grown. Although risk perception and reference to symptoms may suffer from a certain “hysteria” about chemical technology without adequate theoretical evidence (Macgregor & Fleming, 1996), subtle effects on chronically exposed populations are not completely known (Ray, 2000).

     New scientific evidence on ecogenetics, epigenetics, functional teratology and endocrine disruptors suggest that regulatory policies based solely on translational thinking may not be socially viable. To be fully accepted, these procedures should be complemented with collaborative efforts between industry, government, science and society. New toxicity endpoints would have to be studied. Classic behavioral studies would have to be complemented by new methods compatible with adequate experimental environments. Conflict of interests issues should always be properly handled and disclosed. Socioenvironmental responsibility of researchers and healthcare professionals would necessarily increase.

     The social perception of toxic risks associated to the increasing number of chemical agents must be properly faced through effective integration of healthcare, surveillance and intervention. Systematic interdisciplinary and
interinstitutional programs may allow high-quality clinical services, increased scientific production and properly informed decision-making.

     Other questions related to the CI / MCS controversy still have to be thoroughly discussed. Which strategies should one use to establish a productive long-term doctor-CI patient relationship? How can one prevent misogynistic prejudice towards CI patients? How can one adequately communicate risks with poor availability of  information and/or resources? How  can one properly respond to “mass hysteria” episodes? Is cognitive testing CI patients a potentially iatrogenic procedure? And what about alleged harms caused by pharmaceutical drugs in CI patients? Could psychogenic hypotheses be currently being ideologically used to favor certain economic agendas? Is chemical darwinism a legitimate public health concern? Is global feasibility threatened by our currently predatory relationship with environment? Will we have to transform ourselves? If we don’t, isn’t it going to send healthcare to an unsolvable financial deficit? Is true sustainability an unreachable utopia? After all, isn’t MCS the result of a complex cognitive strategy that has been built through human evolution?

     Recently a third clinical approach to CI has been proposed (Engel Jr. et al., 2002), which could be called “mixed” or “neutral”. It proposes an alternative to the ongoing dichotomy and adverts that, as well as avoidance-based therapies, contestation of causal nexus and solely psychiatric approaches could be ineffective or even harmful to patients – and therefore also unethical. By the way, one must always remember Singer (1988) before discharging any patient with unusually bizarre clinical presentations after chemical exposure: the appropriate approach after initial signs of neurotoxicity may avoid debilitating and sometimes permanent nervous system disorders and help to limit the effects of toxic exposure in other organic systems.