What is Multiple Chemical Sensitivity?

Multiple chemical sensitivity is a disorder characterized by recurrent and debilitating symptoms that patients attribute to exposure to low levels of multiple common chemicals. Although its etiopathogenesis is not fully established, hypotheses have been proposed from both pathophysiological and psychogenic approaches.

The etiology of Multiple Chemical Sensitivity remains a subject of debate. Some of the hypotheses include:


Pathophysiological mechanisms:

Central nervous system dysfunction (sensory hypersensitivity): It is proposed that patients present a hypersensitive response in the olfactory and somatosensory systems.

Alterations of the hypothalamus-pituitary-adrenal axis: Dysfunction in stress regulation and homeostasis.

Oxidative stress and cellular damage: Increased free radicals and decreased antioxidant capacity.

Chronic low-grade inflammation: It has been suggested that proinflammatory cytokines may contribute to sensitization.


Psychogenic factors:

Stress, anxiety, and a history of psychological trauma have been associated with the onset of symptoms.

Some authors propose that Multiple Chemical Sensitivity may share characteristics with somatoform or functional disorders.


Predisposing factors:

  • Acute or chronic exposure to chemicals (e.g., solvents, pesticides).
  • Genetic or epigenetic predisposition.
  • Female sex (more frequently reported in women).

Diagnosis:

The diagnosis of Multiple Chemical Sensitivity is clinical and is based on suggested criteria such as those of Cullen (1987) or later adaptations. These include:

  • Recurrent multi-organ symptoms after exposure to chemicals in low concentrations.
  • Identification of specific triggers (perfumes, solvents, tobacco smoke, cleaning products).
  • Exclusion of other medical or psychiatric conditions.

Common diagnostic criteria:

  • Chronic and reproducible symptoms after specific chemical exposures.
  • Improvement of symptoms by avoiding exposure.
  • Multi-organ involvement (respiratory, digestive, neurological, cutaneous systems, etc.).

Exclusion of differential diagnoses including asthma, allergies, food intolerance, autoimmune diseases, psychiatric disorders, among others.

There are no specific biomarkers for Multiple Chemical Sensitivity. Tests are usually performed to rule out other diseases.

There is no curative treatment, and management focuses on symptom control and improving quality of life. Approaches include:


Avoidance strategies:

  • Minimize exposure to identified triggers.
  • Use of controlled environments (e.g., air purifiers).

Medical interventions:

  • Symptomatic treatments according to the affected systems (antihistamines, anxiolytics, antioxidants, among others).
  • Cognitive behavioral therapy can help improve symptom perception.