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Mould Allergy

What is mould allergy?

Moulds are fungi which release tiny particles called spores into the air, and it is these spores that cause allergic symptoms in people when they are breathed in. The black spots on the walls and ceilings of damp rooms are moulds; the white and black furry layers on decaying bread and other foods are moulds. Even mushrooms are a type of fungus!

Mould spores are released all year around and are found in both damp indoor and outdoor environments. Moulds are commonly found in kitchens (fridges), bathrooms, the soil of house plants and in areas where humidifiers and tumble driers are used. Outdoor moulds live in rotting leaves, grass cuttings, compost heaps and rotting seaweed. Moulds love warm humid places and spore counts tend to peak in spring and autumn. They are found in higher concentrations in coastal areas and especially in the subtropical parts of the country (KwaZulu-Natal).

Mould allergy occurs when someone whose immune system is oversensitive sees the mould spores as allergens and reacts to them. People who are sensitive to these mould spores may develop asthma, hay fever, itchy eyes and eczema. Up to 20% of asthmatic patients may be allergic to moulds.

Common allergy provoking moulds in South Africa

  • Alternaria Alternata is found on foodstuffs (as black spots) and in damp indoor areas like bathrooms.
  • Cladosporium Herbarum is the most common allergy-provoking mould in South Africa. It grows indoors in uncleaned fridges, moist windows and window frames, on food and in houses with poor ventilation. It is the most common mould found on dead plants and soil.
  • Penicillium Notatum grows on spoiled food, especially stale bread, cheese, cereals and fruit. One of its good uses is when it is used to make blue cheese. Its levels peak during winter and spring.

Outdoor moulds

  • Penicillium Notatum is both an indoor and outdoor mould, and is commonly found in vineyards and wine cellars.
  • Aspergillus Fumigatus is found in soil, decaying leaves and vegetables, bird droppings and stored sweet potatoes. It is the mould that is associated with asthma and conditions such as Farmer’s lung. Its concentration in the air is relatively low.

Avoiding mould or reducing exposure is the first step to reducing symptoms from mould allergy.

The symptoms of the specific problem can be treated with medication.

Mould control in the home

General control measures

  • Ensure adequate ventilation; closed-up houses prevent the escape of moisture and encourage mould growth.
  • Limit the number of indoor house plants.
  • Dehumidifiers may be used if available (keep indoor humidity at 50% or less).
  • Try to avoid drying damp clothes indoors. Ensure the tumble dryer is vented outside during use.
  • Wipe down mould infested surfaces with bleach or apply mould resistant paint.
  • Wear a mask if working with plant soil or other potential sources of mould.


  • Use extractor fans during cooking.
  • Rubbish bins should be emptied and cleaned frequently.


  • Clean and dry the bathroom surfaces and ensure adequate ventilation.
  • Open the windows after showering or bathing.


  • Replace fitted carpets with wood or tiles.
  • Cover mattress and pillows with mite–proof linen.
  • Remove indoor plants and don’t store food in the bedroom.
  • Dry condensation on windows.
  • Wipe down damp window frames.
  • Air cupboards and never store damp shoes, clothing, luggage or leather goods in cupboards.
  • Curtains, wood panelling and wallpaper may support the growth of mould.
  • Humidifiers and steamers used to treat croup will promote mould growth in the bedroom.
  • A low wattage (40w) light bulb or chemical moisture remover will limit mould growth if placed in cupboards.


  • Allergic people should avoid old grass cuttings and raking leaves. (or wear a mask)
  • Mould spores are worse on dry and windy days.
  • Avoid exposure to soil, compost piles, sandboxes, hay, grapevines and barns.
  • Feed stores on farms are full of moulds.
  • Correct water drainage problems near houses, as pooled water increases mould formation.
  • Avoid camping or walking in forests or densely vegetated areas during autumn and winter months when there are a lot of dead leaves on the ground.
Occupational exposure

Farmers, gardeners, bakers, brewers, florists, carpenters, mill workers, winemakers and wallpaper hangers are at risk for developing mould allergy.

Download our “Mould Allergy” leaflet for free