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Medical Description

The mechanisms and root causes of environmental sensitivities (ES) are not fully understood; however, there has been growing international recognition of the condition over the past six decades.

How a Person Develops ES

The development of ES has been described as a two-stage process: initiation and triggering.

An environmental sensitivity to, or intolerance of, one or more substances previously tolerated starts after an initial acute exposure, illness or injury, or after chronic exposure to environmental contaminants or other demands on the body. For example, a person may develop ES after one large exposure – such as a chemical spill or fire – or after being exposed repeatedly to low or moderate levels of contaminants – for example, as a result of living or working in a “sick building” or recently renovated space.

When a person is subsequently exposed to the offending substance(s), in amounts that were previously tolerated, this can trigger symptoms, which lessen or disappear when she is no longer exposed. These may be substances that the person comes into contact with regularly, like vehicle exhaust fumes, perfume, newsprint, cleaning and laundry products.

A person who initially develops a sensitivity to one substance may later be triggered by a broader range of substances.

A person can be triggered by inhaling (breathing in), ingesting (eating or drinking), or absorbing (touching) the substance.

Common Triggers

Common triggers include:

  • Volatile organic compounds (VOCs), released as gases from gasoline, glues, paints, solvents, perfumes and scented personal care products, “air fresheners,” harsh cleaning products, fragranced detergents and fabric softeners, carpets, furnishings (particularly when new) and some building materials (such as pressed wood)
  • Vehicle exhaust fumes
  • Pesticides (for example, herbicides and insecticides used on lawns and gardens, golf courses, and fruits and vegetables)
  • Pollens from trees, grasses and weeds
  • Moulds
  • Animal dander (for example, from cats and dogs)
  • Electromagnetic radiation (for example, from electric wiring, power lines, computers, televisions and other electrical appliances)
  • Foods (for example, flavourings such as monosodium glutamate (MSG); food preservatives, such as sodium benzoate; colourings, such as tartrazine or FD&C yellow #5; and allergenic foods, like milk, wheat, corn and eggs)

(Note: For reasons that are unclear, in North America there appears to be an increase in reports of anaphylactic reactions to food allergens, which can be life-threatening. These severe reactions most commonly occur to peanuts, tree nuts and shellfish.)

Some people also report developing symptoms when exposed to physical stressors, such as changes in barometric pressure, temperature, light or noise.


The symptoms experienced by people with ES are diverse and can range in severity from mild to debilitating. Some people experience only mild symptoms occasionally, whereas others are seriously disabled by severe symptoms daily.

Symptoms can occur immediately upon being exposed to a triggering substance or several hours later. The symptoms may clear up as soon as the trigger is removed, or persist for hours or even days.

The table below provides an overview of commonly reported symptoms. Symptoms typically affect several body systems at the same time, though sometimes sequentially.

Body System


Central nervous system

Stronger sense of smell than others, feeling spacey, dull or groggy, difficulty concentrating and remembering, headache, restlessness, fatigue, depressed feeling, seizures

Upper respiratory system

Red, watery eyes, stuffy nose, blocked ears, irritated throat, increased infections

Lower respiratory system

Cough, wheezing, shortness of breath, heavy chest

Gastrointestinal system

Heartburn, nausea, bloating, abdominal pain, constipation, diarrhea

Musculoskeletal system

Joint and muscle pain in the extremities and/or back, muscle twitching or spasms, muscle weakness, fatigue

Cardiovascular system

Rapid or irregular heartbeat, cold extremities, high or low blood pressure


Flushing, hives, other rashes, itching

Urinary system

Frequent urination, urgent need to urinate, painful bladder spasms


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Environmental Sensitivities

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