Avoiding moulds indoors and outdoors

What are moulds called?

There are many types of moulds of which the most common are cladosporium, alternia and aspergillus species.

Are they dangerous?

Most are harmless to humans but if found in large amounts then they can cause allergies and breathing difficulties.

Where are moulds found in the house?

Moulds are found in areas that are damp (water in the air) such as the kitchen, bathroom, cellar and around windows. They can also be in washing machines. When we use low temperature wash cycles like 30 degree Celsius, the moulds are not killed off. The seals on refrigerator doors and household plants can also develop moulds on their soil.

What can we do about moulds in the house?

• Ventilate rooms properly by opening windows after having baths or showers.
• In the kitchen having an extraction fan vented outside is helpful but simply opening doors and windows is cheaper.
• Clean out kitchen cupboards regularly to prevent condensation allowing mould growth.
• Put washing machines on a hot wash at least 1 time per week (60 degrees Celsius or above). Also do a wash with household vinegar once per month, leave the door open when not in use and clean out the soap dispenser regularly.
• Clean out the fridge regularly.
• Make sure condensation is dried up on windows to prevent mould growth.
• Check for leaks under any water sources such as baths, sinks and deal with them quickly.
• Change soil in household plants if mouldy.

There is no need to use harsh chemicals in the home environment but good cleaning is important.

Where are moulds found outside?

Moulds have a seasonal variability. There are higher levels in the air in summer and autumn and they can cause acute wheezing in asthmatics, acute allergic rashes, itchy eyes and a runny nose. They are also found under damp leaves, so playing football with leaves or throwing leaves in the air as children do can cause symptoms. Other places such as compost heaps, garden sheds and piles of grass cuttings can become mouldy.

What can we do about moulds outside?

• Be aware that your child has a mould allergy may prevent reactions.
• Encourage children not to play in damp environments such as in heavily wooded areas in the spring and autumn.
• With severe allergy if children want to rake compost heaps then use a face mask.

Types of moulds

The moulds which are most commonly associated with everyday modern living are found most of the year and in similar places. The most common moulds are as follows:

Cladosporium herbarum

Cladosporium herbarum is the most frequently found mould in the air. Indoor concentrations of the spores reflect the outdoor concentration as this mould is easily transported through the air. Levels of this mould rise in the spring and peak in late summer and autumn. Cladosporium is one of the most common colonisers of dead plants and soil. This is the mould that is frequently found on uncleaned refrigerators, foodstuffs, window frames, straw, houses with poor ventilation and in low damp areas. This mould has also been isolated from fuel tanks, face creams, paints and textiles. It is the primary source of mould allergy.

Aspergillus fumigatus

Aspergillus fumigatus is found in soils, leaf and plant litter, decaying vegetables and roots, bird droppings, tobacco and stored sweet potatoes. Compared to other moulds, the concentration of spores in the air is relatively low. However highest levels are found in January and February and a smaller peak in August and September.

Alternaria alternata

Alternaria alternata is the most common habitats for this mould are rotten wood, composts, bird’s nests and forest plants. Black spots on tomatoes and other foods are this mould. This is generally considered to be an outside mould and appears when conditions are warm and hence peaks in July, August and September. This mould is associated with asthma and can cause severe attacks.

Penicillium notatum

Penicillium notatum is widely distributed in soils and can also be isolated from decaying vegetables and leaves. It is found on stored cereals and hay. In house, this mould is the green blue mould found on stale bread, fruits and nuts and it is the mould that is used in the production of blue green mouldy cheese. This mould is present all year round, however its concentrations reach a peak during winter and spring. This mould is associated with indoor allergy.

Download a Monthly mould chart here.

If you’re living in rented or council accommodation and your home is constantly mouldy and damp even after regular cleaning, contact the housing charity Shelter on 0808 800 4444 (calls are free from UK landlines and main mobile networks) or speak to your landlord or housing department at your local authority.