No universally accepted definition exists, but idiopathic environmental intolerance is generally defined as the development of multiple symptoms attributed to exposure to any number of identifiable or unidentifiable chemical substances (inhaled, touched, or ingested) or other exposures in the absence of clinically detectable organ dysfunction or related physical signs.
Immunologic and nonimmunologic theories have been proposed. They are hampered by lack of a consistent dose response to proposed causative substances; ie, symptoms may not be replicated after exposure to high levels of a substance that previously, at much lower levels, seemed to provoke a reaction. Similarly, consistent objective evidence of systemic inflammation, cytokine excess, or immune system activation in relation to symptoms is lacking. Many physicians consider the etiology to be psychologic, probably a form of somatic symptom disorder Somatic Symptom Disorder Somatic symptom disorder is characterized by multiple persistent physical complaints that are associated with excessive and maladaptive thoughts, feelings, and behaviors related to those symptoms... read more . Others suggest that the syndrome is a type of panic attack Panic Attacks and Panic Disorder A panic attack is the sudden onset of a discrete, brief period of intense discomfort, anxiety, or fear accompanied by somatic and/or cognitive symptoms. Panic disorder is occurrence of repeated... read more or agoraphobia Somatic Symptom Disorder Somatic symptom disorder is characterized by multiple persistent physical complaints that are associated with excessive and maladaptive thoughts, feelings, and behaviors related to those symptoms... read more .
Idiopathic environmental intolerance occurs in 40% of people with chronic fatigue syndrome Chronic Fatigue Syndrome Chronic fatigue syndrome (CFS, also called myalgic encephalomyelitis/chronic fatigue syndrome [ME/CFS]) is a syndrome of life-altering fatigue lasting > 6 months that is unexplained and is accompanied... read more and in 16% of people with fibromyalgia Fibromyalgia Fibromyalgia is a common, incompletely understood nonarticular disorder characterized by generalized aching (sometimes severe); widespread tenderness of muscles, areas around tendon insertions... read more . Idiopathic environmental intolerance is more prevalent in women.
Although measurable biologic abnormalities (eg, decreased levels of B cells, elevated levels of IgE) are rare, some patients have such abnormalities. However, these abnormalities appear without a consistent pattern, their significance is uncertain, and testing for these abnormalities to establish an immunologic basis for the disorder should be discouraged.
Symptoms (eg, palpitations, chest pain, sweating, shortness of breath, fatigue, flushing, dizziness, nausea, choking, trembling, numbness, coughing, hoarseness, difficulty concentrating) are numerous and usually involve more than one organ system. Most patients present with a long list of suspected agents, self-identified or identified by a physician during previous testing. Such patients often go to great lengths to avoid these agents by changing residence and employment, avoiding foods containing “chemicals,” sometimes wearing masks in public, or avoiding public settings altogether. Physical examination is characteristically unremarkable.
Diagnosis initially involves exclusion of known disorders with similar manifestations:
Atopic disorders (eg, asthma Asthma Asthma is a disease of diffuse airway inflammation caused by a variety of triggering stimuli resulting in partially or completely reversible bronchoconstriction. Symptoms and signs include dyspnea... read more , angioedema Angioedema Angioedema is edema of the deep dermis and subcutaneous tissues. It is usually an acute mast cell–mediated reaction caused by exposure to drug, venom, dietary, pollen, or animal dander allergens... read more )
Endocrine disorders (eg, carcinoid syndrome Carcinoid Syndrome Carcinoid syndrome develops in some people with carcinoid tumors and is characterized by cutaneous flushing, abdominal cramps, and diarrhea. Right-sided valvular heart disease may develop after... read more , pheochromocytoma Pheochromocytoma A pheochromocytoma is a catecholamine-secreting tumor of chromaffin cells typically located in the adrenals. It causes persistent or paroxysmal hypertension. Diagnosis is by measuring catecholamine... read more , mastocytosis Mastocytosis Mastocytosis is mast cell infiltration of skin or other tissues and organs. Symptoms result mainly from mediator release and include pruritus, flushing, and dyspepsia due to gastric hypersecretion... read more )
Atopic disorders are excluded based on a typical clinical history, skin-prick testing, serum assays of specific IgE, or all 3. Consultation with an allergy specialist may be helpful. Building-related illnesses Specific building-related illnesses (See also Overview of Environmental Pulmonary Disease.) Building-related illnesses are a heterogeneous group of disorders whose etiology is linked to the environment of modern airtight buildings... read more , in which many people who spend time in the same building develop symptoms, should be considered.
If symptoms and signs are not strongly suggestive of a "connective tissue" or systemic autoimmune rheumatologic disorder (eg, joint, skin and/or mucous membrane manifestations), testing for a wide range of autoantibodies (eg, antinuclear antibodies [ANA], rheumatoid factor, extractable nuclear antigens [ENA]) should be avoided. In such cases, pretest probability is low and false-positive results are far more likely than true-positive results; a weakly positive ANA is present in about 20% of the population.
Despite an uncertain cause-and-effect relationship, treatment is sometimes aimed at avoiding the suspected precipitating agents, which may be difficult because many are ubiquitous. However, social isolation and costly and highly disruptive avoidance behaviors should be discouraged. A supportive relationship with a primary care physician who offers reassurance and protects patients from unnecessary tests and procedures is helpful.
Psychologic evaluation and intervention may help, but characteristically many patients resist this approach. However, the point of this approach is not to convince patients that the cause is psychologic but rather to help them cope with their symptoms and improve quality of life (1) Treatment reference Idiopathic environmental intolerance is characterized by recurrent, nonspecific symptoms attributed to low-level exposure to chemically unrelated substances commonly occurring in the environment... read more . Useful techniques include psychologic desensitization (often as part of cognitive-behavioral therapy) (1) Treatment reference Idiopathic environmental intolerance is characterized by recurrent, nonspecific symptoms attributed to low-level exposure to chemically unrelated substances commonly occurring in the environment... read more and graded exposure (see Treatment Treatment Specific phobic disorders consist of persistent, unreasonable, intense fears (phobias) of specific situations, circumstances, or objects. The fears provoke anxiety and avoidance. The causes... read more ). Psychoactive drugs can be helpful if targeted toward coexisting psychiatric disorders (eg, major depression, panic disorder).
Hauge CR, Rasmussen A, Piet J, et al: Mindfulness-based cognitive therapy (MBCT) for multiple chemical sensitivity (MCS): Results from a randomized controlled trial with 1 year follow-up. J Psychosom Res 79(6):628-634, 2015. doi: 10.1016/jpsychores.2015.06.010
Based on current evidence, idiopathic environmental intolerance cannot be explained by non-psychologic factors.
For diagnosis, exclude disorders that can have similar manifestations (eg, allergic disorders) and consider building-related illnesses.
Test for immunologic abnormalities only if indicated by objective clinical findings.
Encourage psychologic therapies such as graded exposure and drug treatment of coexisting psychiatric disorders.