Mould Allergy

Mould is a common form of microscopic fungi that can be found in both indoor and outdoor environments. There are many diverse varieties of mould, each being a multi-celled organism consisting of clusters of branching threads called hyphae that form the mycelium of a fungus. Both mould and yeast are types of fungi but yeast differs because it only consists of single cells that divide to form clusters. As a fungi, mould requires particular conditions to grow, including oxygen, moisture and a ready source of nutrients. Fungi cannot produce food by photosynthesis as other plants do because they lack the green pigment called chlorophyll, which is used to turn water, sunlight and carbon dioxide into complex sugars. Instead, mould feeds on decomposing vegetation or animal matter. Bright sunlight is actually not conducive to the survival of many types of mould, which is why it usually grows in dark, damp areas. The role of mould in nature is to break down dead matter by digesting it.

While moulds are associated with the breaking down of rotten material, some of them are specifically beneficial to humans. Penicillin and other types of antibiotics are produced by moulds, penicillin being a concentrated form of the bacteria-killing toxin manufactured by the penicillium mould. There are other types of mould, however, that can actually cause infection in the same way that bacteria does.

Typically, a mould allergy is triggered when microscopic airborne mould spores are inhaled by someone who is allergic to them, causing them to sneeze or wheeze when they breathe. The symptoms of mould allergy are those usually associated with allergies, including hayfever-like symptoms and respiratory problems. A congested or runny nose, sneezing, coughing, watery or itchy eyes, rashes or hives, and a feeling of fatigue are all possible symptoms. Asthma and sinus infections (sinusitis) can also be caused or exacerbated by the inhalation of mould spores. Sometimes the symptoms of mould allergy can be exacerbated by certain foods. This is especially true of cheeses processed with fungi but can also include mushrooms, dried fruits, pickled or canned food, and food containing yeast.

Mould Spores

Moulds usually reproduce by releasing numerous reproductive particles known as mould spores into the air. These spores are smaller and more numerous than pollen spores but their size, colour and shape can vary greatly between the different types of mould. They have a tendency to "hang" as they waft through the air, which increases the chances that they will be inhaled. Because mould spores are so small, they are often able to evade the protective filtering mechanisms of the nose and the upper respiratory tract. This means that some of the inhaled spores can reach the lungs.

When mould spores come to settle on suitable site they form new mould clusters. New mould growth is prompted by the germination of the spores and the cycle is repeated when new spores are released by the new growth. Most allergy sufferers are not allergic to the mould itself, but only to its spores. The microscopic spores carry mycotoxins, which cause the spores to be allergenic or even toxic.

Like pollen, mould is a common trigger of seasonal allergic rhinitis and this is particularly true if it a time of year when the mould spores are abundant in number. The "mould season" in the US will typically last from spring to late autumn, or fall, peaking from July to late August as more mould and fungus spores become airborne. In autumn, the increased moisture from rain and the drop in temperature increases the growth of mould and fungi. Even though the winter snow will lower the outdoor mould count, it does not eradicate the mould. After the spring thaw, many moulds re-emerge to thrive on the decaying vegetation killed by the winter. As the leaves on the ground rot, more mould spores are released. Mould spores can also be located around hay, compost heaps and straw, even in subfreezing temperatures. Moulds are most prevalent during the humid seasons when plentiful moisture and warmth is present in the environment. In the South and West Coast of the US, for example, some outdoor moulds can be found all year round.

Some mould spores are most abundant at night, especially when it the air is damp, because this is when the process known as "sporulation" occurs. Most mould cannot tolerate direct sunlight, which is why they wait until it is dark to perform this function. People with mould allergy may find their sleep patterns disrupted at night, especially if their air conditioning system only serves to circulate the mould spores around the house. Exposure to mould spores can make the mucus membrane in their nose swell up, making breathing more difficult as the nose becomes blocked. The body responds by releasing adrenalin that makes it more difficult to get to sleep.

Weekly mould counts presented in spores per cubic metre in weather reports can give a relative indication of the amount of mould spores present. Mould spores are compiled by collecting a sample the particulates found in the air and then identifying and counting the relevant amounts of mould spores in the sample. The actual number and types of spores, however, will probably change considerably over 24 hours because of the role the weather plays in spore dispersal. Some moulds release their spores in dry, windy weather conditions while others require conditions of high humidity or the presence of dew to release their spores. Rain will wash some of the bigger varieties of spores out of the air but it can also trigger the release of some of the smaller kinds of spores into the air. Day and night also has an impact on the number of spores present in the air. While nighttime favours the dispersal of wet types of spores, the daytime brings an increase in the number of dry spore types.

Of course, the mould count has little relevance to the amount of toxic mould spores that may be encountered indoors. Staying indoors when the published mould count is high may help to reduce the amount of spores that you inhale but not if you are allergic to a mould that is already present in your indoor environment. In this case, the published mould count will not be particularly relevant to the frequency of your allergy symptoms. Mould can be a perennial problem for those who are allergic to it and can persist despite seasonal changes. Indoor mould can cause perennial allergic rhinitis even in the coldest climates.

There are many places where mould spores are likely to be encountered. This includes fruit shops and places where fresh fruit are stored, secluded damp gardens, potted plants, compost heaps and decaying vegetation, rubbish bins, barns, basements, closets, cellars, attics, garages, house foundations, mattresses, upholstered furniture, old foam rubber pillows, laundries, showers, or anywhere clothes or fabric that may have become damp are stored. Wood products, including paper, wallpaper, and cardboard are all susceptible to mould once they become wet.

Areas that have visible mould, mildew, or a perceptibly "musty" smell should be treated with caution. Certain types of buildings have their own typical set of mould species, with homes, schools, office buildings, bakeries, upholsterers, and breweries all common places to find mould. Some moulds are often found in silos and grain barns where the mould grows on the wheat, barley, oats or corn contained within.

Outdoor moulds are generally less of a threat to the health of humans, except where they are concentrated in outdoor man-made facilities like greenhouses, compost areas and sawmills. Mould can become established if gutters are left neglected, there is excessive moisture buildup, or the drainage of foundation water is inadequate.

Types of Mould

Although there are many diverse varieties of mould, there are only a few dozen types that are known to cause allergic reactions. These include Alternaria and Cladosporium (Hormodendrum), which are the most commonly found types of mould in the United States, both indoors and outdoors. Other common varieties of mould include Penicillium, Aspergillus, Streptomyces, and Mucor. Less common are Epicoccum, Helminthosporium, Rhizopus, and Aureobasidium (Pullularia). Fusarium, Trichoderma, and Stachybotrys are uncommon but potentially very toxic moulds that can grow on water that has been left to stand for a long time. Stachybotrys in particular has received some publicity after being linked to damage to the blood vessels in the lungs of infants.

Alternaria Alternata can usually be found on plants, soils, foodstuffs and textiles. Although it is considered an outdoor mould, this is the mould frequently found on window frames that have condensation. It can also cause black spots on the surface of tomatoes. Associated with warm weather, Alternaria Alternata has also been identified as an important cause of asthma.

Cladosporium Herbarum is another commonly encountered mould. The dry spores, or conidia, of the Cladosporium can be carried through the air over great distances and are increasingly encountered indoors during spring and summer when spore concentrations peak. Cladosporium can be found on dead vegetation, various soil types, on foodstuffs, moist window frames, and refrigerator drip-trays.

The mould Aspergillus grows indoors in damp environments like bathrooms and outdoors in buildings like barns. It can also commonly be found growing on cereal grains. Aspergillus is a type of storage mould that can survive in areas where the level of surface moisture is above 15%. Aspergillus can cause illness, both through infection and allergy. While most people are immune to its effects, some can develop a condition known as Aspergillosis. Aspergillosis is a condition that is encountered worldwide and, in the Northern hemisphere, it is most prevalent during the autumn and winter months. Aspergillosis can result in symptoms ranging from typically hayfever-like allergy symptoms to much more serious, and potentially deadly, generalised infections. One of these conditions is known as Allergic Bronchopulmonary Aspergillosis (ABPA).

The illness ABPA is caused by an allergic reaction to the spores of the mould aspergillus. It is more likely to be contracted by those with pre-existing breathing disorders, like asthmatics or sufferers of cystic fibrosis. Its symptoms are similar to those of severe inflammatory asthma and include coughing, wheezing, a low-grade fever, breathing difficulty, and periodic illness. Diagnosis of ABPA can be obtained using x-rays or tests performed on the skin, blood, and an examination of the sputum of a patient to see if the fungus is present. As the fungus becomes lodged in the airways, it can eventually grow into a compact sphere, or "fungus ball". In some cases, plugs of mucus may be coughed up by a patient. If left untreated, ABPA can lead to serious lung damage and fibrosis as the fungus may spread to the lungs or elsewhere in the body.

Penicillium is the greenish mildew often found in basements, wine cellars and on spoiled food. Like aspergillus, it is a storage mould but it is generally less allergenic than other types of mould. Air conditioners and humidifiers with water storage units can actually spread the mould spores through the air if they become contaminated with penicllium. There is no known relationship between a respiratory allergy to penicllium and an allergy to penicillin, which is derived from the mould.

Stachybotrys chartarum, also known by the synonym Stachybotrys atra, is less commonly found in the home than most of the other types of moulds mentioned above. Stachybotrys is a greenish-black mould with a slimy appearance that grows on surfaces low in nitrogen and high in cellulose. This includes any wood, fibreboard, paper, gypsum board, cotton or dust that remains moist from excessive humidity, condensation, sewer backups, or persistent leaks. Houses with wallboard, sheetrock or cellulose insulation, in combination with a lack of airspace to let the walls breathe, are more likely to have trapped moisture result in stachybotrys. Stachybotrys should not be confused with the greenish mould known as penicllium that is found growing on food like cheese and bread. Stachybotrys has been linked to breathing difficulties in individuals with chronic obstructive pulmonary disorder or asthma and those with compromised immune systems may also be at greater risk from the health complications caused by this mould.

Stachybotrys has received attention because it is believed to cause acute idiopathic pulmonary haemorrhages in infants, although this link has not been definitively established. Pulmonary hemosiderosis produces bleedings in the lungs. In infants under 6 years of age, chronic bleeding can cause breathing difficulties, chronic coughing and congestion with anaemia. Microscopic fungal spores from stachybotrys are believed to carry toxic chemicals called mycotoxins into the lungs of infants, weakening the developing blood vessels. These blood vessels are then considered more prone to bleed due to other irritants and illnesses. The damage caused by stachybotrys has been linked to symptoms as diverse as dizziness, nosebleeds, sleep disorders, and memory loss.

Diagnosing Mould Allergy

There are a number of methods that can be used to help diagnose mould allergy. As with most allergies, consultation with a doctor or allergist will include a discussion of a patient's medical history and possible allergy triggers. Intradermal tests consisting of substances being placed on the arms or dermatitis patches are often used. Detailed testing can also include pulmonary function tests, x-rays of the chest and sinuses, blood tests, nasal smears, and IgE allergy antibody tests.

The skin prick test or a radioallergosorbent test (RAST) can be used to achieve a diagnosis of mould allergy. The skin prick test is the most commonly used test because it is inexpensive to administer and produces immediate results. A RAST test involves collecting blood and can be used in cases where a skin problem makes the use of the skin prick test inappropriate.

Even when these tests produce a positive result, the exact nature of the causative allergen may remain unclear due to variation in the composition of the commercial mould extracts used in the test. This is because commercial tests often use mycelium and metabolic products rather than actual fungi spores, which is the main form in which the allergen is encountered, and each of these forms differs in their protein and allergen content. Another factor is the fact that there are thousands of mould species, far to many to be included in standard allergy tests. If you are allergic to mould it is unlikely that you would react to all fungi because of differences in the spores.

Mould Prevention

One of the indicators of a mould problem in your household is one or more of the occupants becoming constantly sick with respiratory related illnesses, or having an increased incidence of allergic reactions or asthma attacks. Sometimes the smell of mildew will alert you to the presence of mould or it may be visible on particular surfaces. Any mould that is found should be removed and the surface cleaned using household cleaners or bleach. If the surface is made out of an absorbent material, as some ceiling tiles are, then they may need to be replaced rather than just cleaned.

Even the wood used to build your house can make a difference. If the wood used to build a house gets wet before or during the construction of a house, then the chances of the wood developing mould is actually increased. This is one of the advantages of using kiln-dried lumber, along with the fact that it does not warp or shrink as incompletely dried lumber does as it eventually loses it remaining moisture over time.

The way to control mould in the indoor environment is to control moisture, as there is no practical way to eliminate all mould or mould spores. Chronic leaks and wet areas are most likely to be the site of mould growth but some of the hardier moulds can grow in drier environments. Moulds only need a small amount of sustenance to grow and even a little dust in the air conditioning system can provide enough nutrients to sustain mould.

During the hotter months dehumidifiers and air conditioners can be used to control the humidity levels indoors but make sure that you change or clean the filters frequently. Poorly maintained filters can actually become resident to mould. In the winter, exhaust fans and other measures should be used to reduce the chance of too much humidity indoors. Exhaust fans will remove the excess humidity produced by cooking or showering.

Indoors, the humidity should be kept below 40% to hinder the build-up of mould. Air cleaners will be less useful if there is excessive moisture in the air. Fungus will thrive in any indoor environment with over 50% humidity, so aim for somewhere between 45% and 35% humidity. If you are unsure about the current humidity level in your house then a hygrometer can be used to gauge humidity accurately. As well as humidity, many environments have their own particular concerns regarding mould, as outlined below:

Bathroom

With any bathroom, the secret to preventing mould is to keep the area well ventilated and dry. Installing an extractor fan or even something as simple as opening a window can achieve this. This will also help prevent mould growth on the surface of the shower and the walls. Wipe down the shower curtain and shower walls after use and try to keep the curtain dry when the shower is not in use. Use mould-killing solutions on shower curtains, as well as bathroom tiles, the toilet tank and bathroom.

Scour all the sinks and tubs in the bathroom at least once a month. Fungi can also grow on wet soap and the film that begins to coat tiles and grouting over time. Treat problem areas using diluted laundry bleach and make sure that surfaces are given a good scrub. A mixture of one part of chlorine bleach to ten parts of water will provide a suitable bleach solution to clean surfaces with.

Check areas around the bath and basin to make sure there are no leaks or water traps. Repair any plumbing leaks or blocked drains as soon as possible. Remove towels or face cloths that are damp and replace them with fresh ones, especially if they develop a musty odour.

Do not use carpet on the floor of the bathroom because once it gets wet it becomes a source of mould. If carpet has been used to furnish the floor of the bathroom, replace it with linoleum or tiles. Carpet elsewhere in the house that at some time or another has become flooded will need to be removed and replaced.

Laundry

Do not allow damp clothing to remain in the laundry. Instead, dry them as soon as they are washed. If you have a clothes dryer, make sure that it has an external vent connected to the air outside in order to prevent the buildup of dampness inside. Do not leave damp footwear to dry or "air out" in the laundry when they can be left outside and never put clothing or shoes away while they are still wet. Clean the washing machine because mould spores can become attached to the outside of washing machines, contaminating clothing during the spin cycle and causing skin problems.

If the laundry is in the basement, increase the temperature to reduce the amount of humidity present. Small space heaters can be used to heat the basement or low-wattage light bulbs in damp closets can be useful in damp closets. Whatever method you use, be sure to avoid creating a fire risk in the process of keeping areas dry.

Kitchen

In the kitchen, ensure that fruit left in bowls or in the refrigerator has not gone mouldy. Keep an eye on fruit that has been stored at room temperature for more than three days, especially if it is stored in a sealed plastic bag. Do not let bread or other food go mouldy and remove anything before it does. Watch any dried fruit that you have for indications of mould growth. Using airtight containers to restrict the spread of potential moulds. Try to clean rubbish bins and receptacles frequently.

The drip-tray of your refrigerator is another area to watch. Fridges have a ledge that catches excess moisture and then sends it via a pipe to the drip-tray. Both the tray and the pipe used in this system can become mouldy if neglected. To clean this part of the system and prevent mould, put one teaspoon of bleach down the pipe every two weeks. Try to keep the refrigerator door gasket clean as well.

Bedroom

Polyurethane and foam rubber are especially prone to fungus contamination and should be covered in plastic. Some of the allergen proof covers that are available are also waterproof and would also solve this problem. If a foam mattress has previously been wet then it should be encased in plastic because it is likely to contain a considerable amount of mould. This also applies to foam pillows that have become damp from mucus or saliva.

Study or Office

If this is an area where a lot of old newspapers, books, magazines, or piles of papers are stored, they should not be allowed to become damp. If they do, they will most likely develop mildew and a musty odour. In this case, they will need to be discarded or recycled because, even if they dry out, they will still retain mould spores.

Living room

Continuously using an air conditioner or a dehumidifier can lower the moisture levels in the living area enough to prevent mould from growing. The drip-trays of dehumidifiers and air conditioners should be kept clean of mould otherwise they can become contaminated with mould, in which case they may actually worsen mould allergies. Try to clean the reservoirs of humidifiers at least once a week to prevent the growth of mould.

Using central air conditioning with a high efficiency particulate air (HEPA) filter attachment can help to trap mould spores before they are circulated throughout your living area. If you use a vaporiser to dampen the air for someone in the family who has asthma, be aware that frequent use can dampen walls, bedding, and furniture as well. To reduce the chance of mould developing, you should allow as much fresh air to pass through the room as possible or use a dehumidifier.

Check for mildew on any damp walls, especially behind wallpaper. The wall can be treated with paint containing mould inhibitors or treated with a mould inhibitor, a sealer, and then painted. If you have furnishings that contain foam, they can become contaminated by mould if they get damp and will develop a musty smell. Mould can also grow behind furniture and in places where air is unable to circulate. If furnishings become wet, clean and dry them within 24 to 48 hours to prevent mould growth.

If you have plants in your living room, try to keep them to a manageable number, something under ten plants. Do not use plants that have to have a greenhouse-type setting of 20 to 25 degrees Celsius because this sort of environment will result in too much moisture being present. Changing the potting mix of indoor plants regularly will assist the elimination of any mould spores present.

Carpeted surfaces will tend to retain any mould spores that have collected in the house over time. If the carpet becomes damp, it will encourage mould growth. Actually removing carpet that has become mouldy and musty may actually be more successful that trying to have it cleaned. The problem with some cleaning services is that they actually leave the carpet slightly damp and it never completely dries out after the process.

Outside

If an outside area of the house smells musty or looks damp, check that the storm water drain is correctly taking water away from the house. Clean the spouting so that it is working properly and ensure that water is not allowed to run down outside walls. Houses that are completely in the shade will dry out slower than those that enjoy extended periods of sunshine.

Do not allow rising damp to develop in the wall. If it is damp under the house, try to ventilate the area as much as possible. Even thick insulation can be penetrated by mould if vapour barriers in exterior walls are not effective in keeping out the wet. Once mould starts to grow in the insulation of wallboard you will need to replace it.

Remove ivy and other climbing plants from the walls of the house. Try to minimize the amount of vegetation around or over the house, especially near the foundations of the house where dense vegetation will promote dampness.

Keep the grounds of your property free of dead leaves and garden debris. If you have a compost heap, keep it covered and well away from the house. If you use bark and mulches in your garden and around plants, be aware that this will increase the amount of mould that grows there. For the same reason, you should inspect the tree bark of wood for mould before bringing it inside to use in a fireplace or wood-burner stove. For the same reason, some people with mould allergies have problems if they go camping in the woods or stay in cabins that are perpetually wet and encourage mould growth.

Water features on your property should not be much of a problem, provided that the water is kept moving. If not, the water feature will have to be well cleaned and aerated regularly.

Allergy sufferers should try to minimise their exposure to outdoor areas that can potentially harbour mould but if they have to enter these areas then wearing a facemask may help. It may not be aesthetically pleasing but someone with mould allergy should consider wearing a facemask when cutting grass or gardening, activities that are likely to disturb spores. Also, try to avoid gardening during the time of the day when the mould count is at its highest. If you cannot avoid the spores, however, then taking antihistamines and decongestants will help with the symptoms of mould allergies.