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Home / Indoor air quality-which allergens are found in the home?

Indoor air quality-which allergens are found in the home?

by | Nov 18, 2019 | Air Quality, Food Allergy

Indoor air quality-which allergens are found in the home?


Outdoor air quality has been well studied but many hours are spent indoors so it is important to look at the quality of the air that we breathe inside buildings. Indoor air content will reflect the outdoor air around the building, whether it is a home, school or office but the aeroallergens in every home are unique to that home. The aeroallergens in a home depend on the lifestyle of the homeowner as well as the quality of the air outside the home.

Say no to smoking indoors

Particulate matter (PM) is found in outdoor air and the amount and size of PM depends on the source. Particulate matter suspended in the air is derived from burning coal and it is found close to large roads where the source is diesel exhaust fumes. PM increases after fires when tiny fragments of debris become airborne, but the smallest sized particles are released from tobacco smoke. These tiny particles reach deep into the lungs and for this reason smoking indoors should be discouraged, especially in the homes of allergy sufferers. This applies especially to asthmatic children.

House dust mite and cockroach allergens

The eight-legged house dust mite belongs to the class Arachnida, along with spiders. They live indoors and are found in high numbers on carpets, fabric upholstery and especially on mattresses. House dust mite numbers can be reduced by covering mattresses with mite proof covers, replacing carpets with hardwood, tiled or vinyl floors and removing soft toys from children’s bedrooms. Mites prefer humid environments so drying the air, by using heaters in winter when possible, will discourage these allergenic insects from taking up residence in the home. House dust mites are the most important of the indoor allergens, but cockroaches are also allergenic and readily invade homes and other buildings, especially in coastal cities. They prefer to live in warm, humid environments but cockroach bait and fumigation will eliminate these pests from buildings. There are tests to measure indoor house dust mite levels overseas but these are not available in South Africa.

Pets in the home

Cat, dog and hamsters in the home add to the allergen content off the air so keep these pets out of the bedrooms of any family member who reacts to their allergens. Where this is not possible, frequent washing of bedding may help, but It is often the small airborne saliva droplets that trigger reactions when they are inhaled and for this reason pet free zones in the home are advisable.

Indoor mould

Moulds or fungal spores are opportunistic and grow best on organic material in warm, humid environments. Some moulds will grow at very low temperatures and may even grow well inside fridges, but bathrooms and kitchens and damp walls are the most common places to find mould growth. Some mould spores are extremely allergenic so patches of mould should be kept in check by wiping down tiles with a dilute solution of bleach, washing shower curtains and keeping refuse containers and kitchen cupboards clean. Discard any rotting fruit or contaminated food, like bread. Remove old leaves from indoor plants and cover the soil of pot plants with small stones. Succulents are a better choice of indoor plants in offices where large trees and shrubs may be displayed, as their pollen is seldom allergenic.

Testing indoor air quality

In Europe and North America, testing services identify and count the number of colony forming units (CFU) to estimate indoor mould growth. There are few such services in South Africa, but some food safety testing services will conduct tests to identify mould in indoor air by exposing agar plates, known as ‘settle plates’ to culture and identify fungal spores in the air.


Buildings with poor airflow may develop ‘sick building syndrome’ where an unacceptably high number of mould spores are found. Maintain good air flow and where windows are closed or sealed and air conditioners are used, be sure to clean the filters regularly. If seasonal pollen allergy is suspected, close the windows that open onto vegetation and use a painter’s mask when mowing grass.


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