Idiopathic environmental intolerance is characterized by recurrent, nonspecific symptoms attributed to low-level exposure to chemically unrelated substances commonly occurring in the environment or sometimes to hypersensitivity to electromagnetic fields. Symptoms are numerous, often involving multiple organ systems, but physical findings are unremarkable. Diagnosis is by exclusion. Treatment is psychological support and avoidance of perceived triggers, although triggers rarely can be defined.
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 (1).
General reference
1. Idiopathic environmental intolerances. American Academy of Allergy, Asthma and Immunology (AAAAI) Board of Directors. J Allergy Clin Immunol. 1999;103(1 Pt 1):36-40.
Etiology of Idiopathic Environmental Intolerance
Triggers
Reported triggers for idiopathic environmental intolerance include
Alcohol and medications
Carpet and furniture odors
Fuel odors and engine exhaust
Painting materials
Perfume and other scented products
Pesticides and herbicides
Mobile telecommunication devices
Mechanism
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 psychological, probably a form of somatic symptom disorder. Others suggest that the syndrome is a type of panic attack or agoraphobia.
Idiopathic environmental intolerance occurs in 40% of people with chronic fatigue syndrome (also called myalgic encephalomyelitis/chronic fatigue syndrome [ME/CFS]) and in 16% of people with fibromyalgia (1). 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.
Etiology reference
1. Jason LA, Taylor RR, Kennedy CL: Chronic fatigue syndrome, fibromyalgia, and multiple chemical sensitivities in a community-based sample of persons with chronic fatigue syndrome-like symptoms. Psychosom Med. 2000;62(5):655-663. doi:10.1097/00006842-200009000-00009
Symptoms and Signs of Idiopathic Environmental Intolerance
Symptoms of idiopathic environmental intolerance (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 of Idiopathic Environmental Intolerance
Exclusion of other causes
Diagnosis of idiopathic environmental intolerance initially involves exclusion of known disorders with similar manifestations:
Allergies (eg, allergic rhinitis, food allergies)
Atopic disorders (eg, asthma, angioedema)
Endocrine disorders (eg, carcinoid syndrome, pheochromocytoma, mastocytosis)
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, 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 systemic rheumatic disease (eg, objective joint, skin, and/or mucous membrane manifestations), testing for 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.
Treatment of Idiopathic Environmental Intolerance
Sometimes avoiding suspected triggers
Psychological treatments
Despite an uncertain cause-and-effect relationship, treatment of idiopathic environmental intolerance 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.
Psychological evaluation and intervention may help patients overcome some avoidant behaviors (1), but characteristically many patients resist this approach. The point of this approach is not to convince patients that the cause is psychological but rather to help them cope with their symptoms and improve quality of life (2). Useful techniques include psychological desensitization (often as part of cognitive-behavioral therapy) (2) and graded exposure (see Specific Phobic Disorders, Treatment). Psychoactive medications can be beneficial if targeted toward coexisting psychiatric disorders (eg, major depression, panic disorder).
Treatment references
1. Binkley KE: Multiple Chemical Sensitivity/Idiopathic Environmental Intolerance: A Practical Approach to Diagnosis and Management. J Allergy Clin Immunol Pract. 2023;11(12):3645-3649. doi:10.1016/j.jaip.2023.08.039
2. 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
Key Points
Idiopathic environmental intolerance cannot be explained by non-psychological factors.
For diagnosis, exclude disorders that can have similar intermittent manifestations (eg, allergic disorders) and consider building-related illnesses.
Test for immunologic abnormalities only if indicated by objective clinical or laboratory findings.
Encourage psychological therapies (eg, desensitization, graded exposure) and coping skills; pharmacological and behavioral treatment of coexisting psychiatric disorders may also be beneficial.
