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Health problems caused by mould


Mould is a fungus whose spores are invisible to the naked eye. It can form colonies in various parts of a building where there is:

  • Excess water or moisture
  • A sufficient amount of nutritive material such as cardboard or drywall

When it appears in a small area and is cleaned up quickly, mould is generally not a particular problem. When it grows significantly, however, mould releases particles into the air that can lead to health problems when inhaled. 


There are a variety of symptoms that can be associated with exposure to mould. Each person can react differently depending on the degree of exposure and his or her general health. The main symptoms are the following:

  • Irritation of the eyes, nose and throat
  • Runny nose, sinus congestion, symptoms similar to those of the common cold
  • Wheezing
  • Coughing
  • Increase in frequency and severity of asthma attacks
  • Chronic fatigue and headaches

It is important to remember that symptoms can also be caused by other types of indoor air contaminants, including:

  • Tobacco smoke
  • Mites
  • Volatile organic compound, mainly formaldehyde from household products (paints, varnishes, etc.) and construction materials (chipboard, plywood panels, etc.)
  • Allergens from the saliva and fur of domestic animals
  • Particles suspended in the air from wood heating or cooking appliances

When to consult

If you think that your symptoms or those of a family member may be caused by mould, see a health-care professional or call Info-Santé 811.

People at risk

Some people are at higher risk of developing health problems when exposed to mould. They include:

  • People with allergies
  • People with asthma or other chronic respiratory diseases
  • Infants and young children
  • Seniors
  • People with a weakened immune system (e.g., due to chemotherapy or a recent organ transplant)

Protection and prevention

You can take certain precautions to avoid being exposed to mould and developing the associated health problems.

Preventing the development of mould in your home and knowing how to spot it are important. To do this:

  • Inspect all rooms in your home regularly and repair any water damage or infiltration. Clean and dry it within 24 to 48 hours.
  • Make sure that your home is properly ventilated, especially during activities that produce a lot of humidity, such as when taking a bath or shower or cooking.

For more advice, read Finding and eliminating mould from your home.

Last update: November 30, 2022


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