Allergens: Moulds and Other Fungi
Moulds and Other Fungi
The air around us is full of bits and pieces that are mostly too small to be seen without a microscope - pollen grains, mould spores, fragments from plants, fibres from clothing, specks of ash from smoke, skin flakes and diesel particles. Of these, mould spores are by far the most abundant.
Except in very dry climates, there are more mould spores in the air than anything else. In Britain the record count is over 160,000 spores per cubic metre of air, compared to a record pollen count of only 2800 grains per cubic metre. Luckily, mould spores are not particularly allergenic or even more people would be suffering as a result of inhaling such huge quantities of them.
Spores are produced by moulds and other fungi, and they are to the fungus what seeds are to a plant – they can grow into new fungi. Doctors generally speak just of ‘mould allergy’ because moulds are the most common offenders, but larger fungi – mushrooms and toadstools – also produce allergenic spores. For example, a bracket fungus called Ganoderma, that infests dead trees and produces spores prolifically in mid-June, has been found to affect 16% of asthmatics in one part of New Zealand. Bracket fungi occur all over the world, but until recently no one had suspected them of causing allergic reactions, so the extent to which they cause allergies has not been investigated. The same is true of other large fungi.
Yeasts (single-celled fungi) are also found in the air, and it is possible –though this has not been investigated – that people with an allergy to yeast in food would also react to inhaled yeasts.
Indoors and out
Mould spores are a particular nuisance because they can be produced both indoors and out. There are different species of mould in different places, and you may be lucky and only react to one or two uncommon species. But many moulds grow in a very wide range of situations, both indoors and outdoors. There are also cross-reactions (see p. 14) between some of the moulds, unfortunately, which means that people generally react to a great number of different moulds. You will probably need to reduce mould growth inside your home as well as avoiding mould-rich places outside. Changes to your garden that eliminate havens for moulds, such as leaf piles, may also be helpful.
Moulds may only be growing in one part of a house – the cellar perhaps – but can be carried all around the house on air currents.
The size of the allergen particles
Most mould spores are between 2 and 10 microns in size. A few species have spores that are smaller than 2 microns.
(A micron is one thousandth of a millimetre.) Some people with mould allergy may be protected by an ordinary dust mask (see p. 109), but most will probably need a better-quality mask.
Avoiding outdoor moulds
Moulds live in the soil, and grow on any decaying plant matter, such as dead leaves, dying plants, fallen trees, hay and straw. Spore counts are highest in the autumn. A thick covering of snow reduces the numbers of mould spores in the air dramatically. Once the snow melts in spring, moulds flourish on the plants killed by the cold, so spore counts soon rise again.
The effect of the weather on spore release is very complex. Some moulds like to release their spores when it is dry and windy, but others favour fog, mist or dew. Rainfall washes a lot of spores out of the air, but it stimulates the release of some small spores.
A few pollen information services also give current mould-spore counts, but predicting spore counts for the following day is well-nigh impossible.
Drastic avoidance measures, for those who are severely sensitive, include moving to a desert or semi-arid area where there are far fewer mould spores in the air.
Listed below are the mould-rich situations and activities which could provoke your allergy symptoms. If they do, you should avoid them, or wear a mask that will prevent the spores being inhaled (see box on p. 120).
Places
• Near fields of cereal crops in late summer, because of moulds growing on the cereal leaves. Symptoms are likely at harvest time, when combine harvesters disperse the spores.
• In forests and old orchards, in gardens with compost heaps or piles of dead leaves, and in greenhouses.
• Near springs, waterfalls, and other damp, shady places.
Times
• During late summer and autumn, when moulds flourish outdoors on fallen leaves and fruit.
• Following the first frost of autumn, which triggers spore release by fungi in the soil.
Activities
• Disturbing compost heaps, damp straw or hay, piles of grass clippings or heaps of fallen leaves, all of which are absolutely full of moulds.
• Collecting up fallen leaves or fruit.
• Watering the garden because mould spores are released when water hits the dry soil.
• Mowing grass, if the clippings were not cleared up after the last mowing. Unless the weather is very dry, the clippings tend to go mouldy.
• Removing dead leaves or flowers from plants.
A dangerous mould allergy
Anyone with asthma who also has allergy to the mould Alternaria should –with their doctor’s agreement – increase their dose of preventer inhaler (e.g. steroid or cromoglycate) during the spore-producing season. Research shows that severe near-fatal asthma attacks often occur during the Alternaria spore season among those allergic to this mould.
Spore release by Alternaria usually occurs in the summer or autumn, but the timing varies from one part of the world to another, so check with your doctor or a local pollen/spore monitoring service. Alternaria can live outdoors in soil, and on seeds and plants. Indoors, it is a denizen of window frames, carpets and textiles.
Indoor moulds
These are the indoor situations that can be difficult for mould-sensitive people. You should either avoid these, wear a mask, or tackle the problem at source – for example, by reducing dampness (see p. 119).
Places
• Buildings that are damp, because moisture encourages mould growth. Never sleep in a room which has mould growing on the walls or window-panes. In addition to damp houses – now very common – you may encounter moulds in old churches and church halls.
• Buildings that are near lakes, rivers or the sea, because of the dampness of the air. Rooms with humidifiers.
• Bathrooms and shower rooms, unless well ventilated, owing to the steam and condensation.
• Rooms that are generally left unheated, and are therefore colder than the rest of the house, as these tend to suffer from condensation.
• Buildings with dry rot or wet rot. Not all mould-sensitive people react to the spores of these dreaded timber-rotting fungi, but some do.
• Buildings where old timbers are being removed, as this stirs up huge numbers of spores.
• Buildings where central heating has recently been installed, as the warmer temperatures in the building stimulates the existing moulds to release their spores.
• Buildings with lots of indoor plants. There are moulds you cannot see growing on the surface of the soil around a potted plant.
• Cellars and basements. Conservatories can also be full of moulds if not well maintained.
• Antique shops, farms, mills, holiday cottages.
On the first day of Christmas…
Christmas trees usually have moulds (which you can’t see) growing on the needles. When the tree is brought indoors, the warmth encourages these moulds to shed their spores.
Times
• During the winter, when there are usually more moulds growing indoors due to condensation.
Activities
• Handling clothes, curtains or furnishings that smell mildewy: they may be dry now but they will still be full of mould spores.
• Handling vegetables or fruit that have been stored a long
time, or in damp conditions (e.g. in plastic wrapping). Note
that this can include mushrooms – they often have white
moulds growing on them, which can be quite inconspicuous. If looking around your house for moulds, bear in mind that they vary a great deal in colour. Bread, vegetables, cheese and other foods that are past their best grow green, grey or white moulds, often furry, and these are the ones most people are familiar with. But the black stuff on the walls of bathrooms and in the door seals of refrigerators is also mould. In some situations it takes a practised eye to spot this type of mould – around window frames for example, or in the patterns of bathroom-window glass, it can easily be mistaken for ordinary dirt. On shower curtains and cubicles you may find pinkish-red moulds as well as these black kinds. Garden plants and crops can have bright orange moulds (called ‘rusts’) on their leaves, as well as the more familiar grey or black kinds.
Combating indoor moulds
The crucial task here is to reduce dampness and condensation in the house – see p. 119 for the details – as this encourages mould growth on all kinds of surfaces, including walls, ceilings, windows, bathroom tiles, shower curtains, and even carpets. Once you have reduced the humidity, then you can have a big clean-up and remove the spores that have been left by moulds.
If your allergy symptoms are very bad, and you need some immediate relief, then you could get someone to clean away the mould growth and spores first, then tackle the damp problem, then repeat the cleaning operation. Obviously, this is less efficient, but it may be the best approach if you are severely affected.
Note that the cleaning will, in itself, stir up a massive but unseen cloud of spores, so the allergy sufferer should not be at home during this work (see p. 109).
Cleaning away moulds and stopping regrowth
There are two aspects to this task:
• a one-off effort to clear the accumulation of mould growth and old mould spores – trillions of them are probably lying around your house – since these spores are the cause of the allergic reaction
• an ongoing effort to prevent the regrowth of moulds in problem areas such as the bathroom.
Get rid of any furniture that smells ‘mildewy’: it is packed with old mould spores. Fabric items that have this smell should be washed thoroughly. Old clothing, books and newspapers may also be a source of mould spores.
Any carpets or other porous materials (e.g. ceiling tiles, wall panels) that have ever been soaked by flood or storm waters should be disposed of now – and, unless everything can be dried within 24 hours, this should be always be done if there is water penetration in the future. Research shows that such materials quickly become infested with moulds. Check above the flood line, as water can seep upwards through the walls or panelling.
On fridges and freezers, clean out the rubber seals around the doors, going into all the crevices to get out the black mould that lives there. Also clean out the drip-pans of fridges, freezers and dehumidifiers. Keep shower heads and air conditioning equipment (including the filters) very clean. This all needs to be done regularly from now on.
Clean off all the mould growing around windows, or on walls and ceilings, tiles or other surfaces. Alcohol (e.g, white spirit or surgical spirit) kills it very effectively, without the use of water, and it takes a long time to grow back again. You could, alternatively, wash down the walls with a mix of one part bleach to two parts water. (But note that chlorine fumes may be irritating to the airways of those with rhinitis or asthma.) Special anti-mould sprays are also available, but try them out cautiously as they too may be irritants. Do not brush mould growth off with a dry cloth, as this simply disperses the spores. In the future, keep an eye out for new mould growth, and remove it promptly.
Buy a new shower curtain and replace it regularly, or clean it thoroughly with an anti-mould spray.
Can foods and mould spores cross-react?
Some people with mould allergy appear to be affected by eating mushrooms, or foods that contain yeasts or other fungi, e.g. certain well-ripened cheeses, dried fruit, soy sauce and vinegar. There has been little scientific investigation of these claims.
No cause for concern
The drug penicillin – which can cause severe allergic reactions – comes from the Penicillium mould. Fortunately, there appears to be no cross-reaction between the drug and the spores of Penicillium.
Cut down on the number of houseplants, and find a new home for any that need constant moisture. With the remaining plants, take off dying leaves and flowers promptly, and remove the top layer of soil occasionally, replacing it with fresh soil or – even better – sand or grit. Pot-pourri should also be evicted, as it can be full of mould spores.
Use vegetables and fruit promptly, and do not allow bread to go stale, or jam to go mouldy.
What to do if these measures fail
Where there is an invincible damp problem, a really powerful dehumidifier used during the day in bedrooms, and at night in the sitting room, will kill off most moulds and defeat their efforts to regrow. Close all the doors and windows in the room where the dehumidifier is operating, and shut off air vents. Note that air conditioning will also reduce the humidity of the air, but not as much.
Keeping mould spores out of the airways
Ordinary house dust can contain a lot of mould spores. The allergic individual should not dust, vacuum clean, sweep floors or make beds until the anti-mould measures have begun to bite. Ideally the allergic person should go out while housework is done, and the house should be thoroughly aired before their return. If this is impossible, then wearing a good mask all the time is essential. A special vacuum cleaner that retains allergens, or vents them outside. may be helpful in addition to the mask.
Even though you have cut down on moisture and condensation, and tackled mould growth, there could still be a lot of mould spores around, especially in an old house, one that has been very damp in the past, or one that is close to water. If symptoms persist, then think about hiring or buying a high-quality HEPA air filter (see p. 108) to take mould spores out of the air.
Do not use fans or fan heaters, as these churn up mould spores from the floor and other surfaces.
Beating athlete’s foot
Allergenic fungi can grow on your body, as well as in your house (see pp. 16-17). If athlete’s foot is playing a part in your allergies, it is vital to treat the infection thoroughly with drugs, because the fungus grows deep into the skin and can quickly stage a come-back if not completely destroyed. You should also be careful not to reinfect yourself:
• always dry your feet very thoroughly, especially between the toes; kitchen roll does a better job than towels, and can be discarded, reducing the risk of re-infection
• wear cotton socks and shoes made of leather or canvas, which allow sweat to evaporate; only wear trainers or gumboots, or any other footwear that makes your feet feel sweaty, when you really need to
• when your feet get wet, change your socks and shoes promptly
• launder all towels and bath mats at high temperatures when you start the course of anti-fungal drugs, and again when you complete it
• never share towels, bath mats, socks, sandals or shoes
• wear flip-flops at the swimming pool or sauna, and in changing rooms; if any other member of the household has athlete’s foot, take the same precautions in the bathroom at home – and make sure they seek treatment.
Occasionally athlete’s foot is a misdiagnosis for atopic eczema of the feet, which is a common problem among allergy-prone children (see box on p. 45). If the skin between the toes is not affected, it’s unlikely to be athlete’s foot and more likely to be eczema.