Multiple Chemical Sensitivity (MCS)

What we know

Multiple chemical sensitivity, sometimes called environmental sensitivities or idiopathic environmental intolerance, describes recurring symptoms triggered by low-level exposures to many unrelated substances. Symptoms often include headache, fatigue, difficulty concentrating, breathing or throat irritation, nausea and skin reactions.

There is no agreed laboratory test for chemical sensitivity, and researchers still debate its causes. In Canada, environmental sensitivities are recognized in human rights guidance as a disability that may require accommodation.

Where genetics fits

Your body processes many substances through "detoxification" pathways, enzymes that change compounds so they can be removed. Genetic differences in some of these enzymes have been studied in people with chemical sensitivities, but the results have been inconsistent.

Practical steps people often find helpful

• Track exposures and symptoms to spot patterns
• Reduce exposures at home, for example with fragrance-free products and good ventilation
• Ask your workplace or school about accommodations if needed
• Work with a clinician to rule out other causes, such as asthma, allergies or MCAS

Curious about mould-related exposures? Read Mycotoxin Exposure & Testing.