ME/CFS causes heightened sensitivity to environmental stimuli.

These stimuli can initiate specific symptoms and may trigger post-exertional malaise (PEM), with an exacerbation of all symptoms and a deterioration in functional capacity.
In addition to the impact of individual stimuli, it is important to recognise the impact of the total load of environmental stimuli.

Even low levels of stimulation can result in mild to severe reactions. The severity of symptom exacerbation is out of proportion to the intensity and duration of the stimulus.

The highest endorsed non-exertion triggers [of PEM] reported by participants were as follows: emotional events (88.3%), noise (85.5%), and sensory overload (83.6%).

C S Holtzman, S Bhatia, J Cotler, L Jason, diagnostics, 2 March 2019, p11

Physical stimuli

  • touch (allodynia)
  • light (photophobia)
  • noise (hyperacusis)
  • pressure (hyperalgesia)
  • temperature changes or extremes
  • vibrations/movement


Lifestyle adaptations can reduce the total stimulus load, for example, spending time in a quiet, still, dimly lit place; wearing comfortable clothing; choosing less-busy times or dedicated sensory-friendly sessions to go to supermarkets or elsewhere.

Ingested stimuli

ME/CFS may cause or exacerbate sensitivities and intolerances to foods, medications and nutritional supplements.


Foods: it may be helpful to explore an elimination diet under the supervision of a dietician experienced in ME/CFS.

Medications and supplements: start with a low dose since the usual doses are often poorly tolerated.

Inhaled stimuli

ME/CFS may cause or worsen sensitivities and intolerances to very low levels of inhaled substances. Reactions can range from mild to severe, leading to PEM and even long-term relapses. Problematic inhaled substances may include:

  • perfumes and fragrances, including essential oils and synthetic forms, that may occur in products such as shampoo, deodorant, laundry detergent, disposable nappies
  • cosmetics, including unscented hairspray and skin care products
  • cleaning products
  • upholstery, carpeting and building materials, including formaldehyde from manufactured wood
  • paints, adhesives, solvents
  • organophosphates, including pesticides, insecticides and herbicides
  • petrochemicals, including exhaust fumes from vehicles and natural gas appliances
  • ozone, including from printers, copy machines, and ozone air purifiers
  • printing ink
  • smoke

Multiple chemical sensitivity

People who experience reactions to low levels of a number of different common chemicals are said to have multiple chemical sensitivity (MCS).


Strategies for managing sensitivities to inhaled substances include avoiding risky environments, wearing a mask, and improving indoor air quality by using air filters, air conditioning systems and opening windows.

Where possible use low-emitting building materials and products, such as VOC-free paint; allow furniture and other goods time to release fumes (outgas) before use; and ask others to reduce their use of fragrance.

Biological stimuli

Some naturally occurring substances, including biotoxins and low levels of biological contaminants that are not normally considered toxic, may be poorly tolerated by a person with ME/CFS.

The most commonly reported example is mould. There are many types of mould to which individuals may react in different ways.


The Centers for Disease Control and Prevention (CDC) in the United States has provided a comprehensive guide to understanding and dealing with mould problems.

Australian National Register of Environmental Sensitivities

People with environmental sensitivities are encouraged to register with the Australian National Register of Environmental Sensitivities (ANRES).

Last edited: 14 December, 2021