Mold allergy symptoms can be defined as damaging immune responses by the body to mold and/or mold byproducts.

Molds are microscopic fungi characterized by having a body structure made up of thin branching thread-like filaments. Mold spores and fragments contain irritating substances called allergens that trigger allergy reactions.

Some also produce toxic substances called mycotoxins that are well documented for their health effects. Individuals who are most likely to show mold allergy symptoms are people who are sensitive to molds. Mold exposure primarily occurs when people inhale airborne mold spores and/or fragments. Exposure may also occur through skin contact.

Mold allergy symptoms may be difficult to isolate from allergies caused by other allergens such as pollen, insect parts, animal hair and chemicals.

Mold allergy symptoms may show up immediately or after a period of time following mold exposure. Both dead and viable spores may lead to allergic reactions. That’s killing mold with chemicals without removing it is not recommended. Common symptoms include sneezing, runny nose, coughing, wheezing, tearing and redness of the eyes, and skin irritation or rash. Mold exposure can also exacerbate asthma attacks in people who have a history of asthma and are allergic to mold.

There are hundreds of types of molds but not all of them are responsible for causing allergy symptoms. The common mold spore types known to cause allergy and asthma in many parts of the world are Alternaria, Cladosporium, Aspergillus, Penicillium and Didymella.

Allergic reactions to each spore type may differ between individuals and the allergens vary in the severity of the allergic reaction they induce. For example, it has been observed that more people are allergic to Alternaria than Cladosporium even though the latter is much more common in the air. Alternaria also produces stronger positive reactions while Cladosporium tends to produce a milder allergic reaction.

However Cladosporium, and in particular Cladosporium herbarum, is often the major contributor to air-spora and due to its high concentrations is therefore a major cause of inhalant allergy and allergic asthma in humans. Didymella exitialis can trigger severe asthma and it cross-reacts with Alternaria. Didymella exitialis is common on cereal crops, particularly wheat and barley so the risk can increase around harvesting of these crops.

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Mold exposure at home and the workplace can cause allergy in susceptible individuals. Mold allergy symptoms may be difficult to isolate from those caused by other allergy triggers (allergens) such as pollen, dust mites, cockroach allergens, animal allergens (hair, dander, saliva) and chemicals.

Pollen is generally an outdoor problem although it could, in summer, infiltrate into the indoor environment from outdoors. Pollen is produced outdoors by weeds, grasses and trees. The allergens must be inhaled in order to cause respiratory allergy symptoms.

Mold Allergy Symptoms

There are hundreds of types of molds, but not all of them are responsible for causing allergy symptoms. The range of mold allergy symptoms in susceptible individuals may include sneezing, runny nose, mucous production, cough, congestion, sinusitis, earache, headache, wheezing, and asthma.

It is estimated that about 3-4% of the human population and 10% of atopic people get symptoms from exposure to mold spores while the majority of severe asthma sufferers are allergic to them. A number of mold spore types have similar allergens which mean that those who are allergic to molds are likely to be sensitized to multiple types.

Since different molds release their spores at different times of the year, some people can be affected for large parts of the year. It is difficult to say how much mold is too much as human reactions to allergens can vary greatly depending on individual sensitivity. The length of exposure to mold, the amount of allergens, and individual sensitivity determines the severity of the allergy symptoms.

The higher the exposure to mold spores the greater the number of people that would react. The allergic effect of mold spores and pollen does not depend on whether the mold spores or pollen grains are dead or not.

Common Mold Allergy Symptoms Triggers

The commmon mold spore types that trigger allergy and asthma in many parts of the world are Alternaria, Cladosporium, Aspergillus, Penicillium and Didymella. Allergic reactions to each spore type differ between individuals and the allergens vary in the severity of the allergic reaction they induce.

For example, it has been observed that more people are allergic to Alternaria than Cladosporium even though the latter is much more common in the air. Alternaria also produces stronger positive reactions while Cladosporium tends to produce a milder allergic reaction.

However Cladosporium, and in particular Cladosporium herbarum, is often the major contributor to air-spora and due to its high concentrations is therefore a major cause of inhalant allergy and allergic asthma in humans.

Didymella exitialis can trigger severe asthma and also cross-reacts with Alternaria. Didymella exitialis is common on cereal crops, particularly wheat and barley so the risk can increase around harvesting of these crops.

How Does One Get Exposed To Mold Spores?

Since mold spores are everywhere exposure occurs all the time whether we’re at home, workplace or outdoors. Mold spores may enter indoors from the outside through open doorways, windows, and heating, ventilation, and air conditioning systems with outdoor air intakes. People can also bring mold spores indoors on their clothing, shoes, bags, and pets.

People are primarily exposed to molds by inhaling airborne spores. They could also be exposed to mold toxins (mycotoxins) by touching mold or eating contaminated food. Because molds are naturally found outdoors and indoors, living in a totally mold-free environment is practically impossible.

In Conclusion

It is generally agreed that mold is a health hazard and exposure can happen at home, in the workplace or outdoors. However, media “hype” about mold often creates unnecessary concern about exposure to mold. At times people may attribute a wide range of symptoms and even serious illnesses to exposure to mold in their home or workplace, even when there is no active indoor mold growth.

It is important that any person experiencing serious symptoms to discuss their concerns with their family doctor as sometimes the symptoms may not be related to mold exposure.

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However, dampness itself may have no or little direct effect to allergy development. Dampness only favours proliferation of biological and increased emission of chemical pollutants. A strong association has been found between exposure to visible mould and asthma and common colds.

Studies have also shown that the risk of asthma in damp homes is highest among individuals with hereditary allergy.

Causes of dampness in a building may be complex. Possible causes may include:

• Penetrating damp due to defects in the roof, walls or plumbing
• Rising damp
• Condensation
• The activities of the building’s occupants such as cooking, dishwashing, and cleaning.

How Does Dampness Contribute to Increased Asthma and Allergy Risks?

Dampness contributes indirectly to asthma and allergy risks. Increase in humidity in the building encourages proliferation of moulds, bacteria, house dust mites, and other micro-organisms some of which are toxin producers or allergens. Dampness also results in increased emission of chemical pollutants from degrading building materials.

Mould spores are generally everywhere. Nutrients are also available in form of organic dust or cellulose found on most building surfaces. In most cases the limiting factor to mould growth in a building is moisture. Moulds have a minimum level of dampness (relative humidity) below which growth is limited. Generally relative humidity below 65% restricts mould growth.

Dampness is also essential for the survival of house dust mites. Since house dust mites do not drink free water they absorb it from the air and the environment. House dust mites feed on human skin scales (flakes), pollen, moulds, bacteria, animal dander, and skin scales of birds. These food sources have to be moist for mites to utilize them.

Therefore, the food consumption of mites increases (and hence their population) at high relative humidity. It has been estimated that human beings shed dead skin at a daily rate of 0.5-1.0g per person and several thousand mites can survive for months on just 0.25g, so moisture and not food would be the limiting factor to mite proliferation. House dust mites survive best at relative humidity of 70-85% and temperatures of 24-27 °C.

The Interaction Between Moulds, Other Micro-organisms and Mites

Mites help in dispersal of bacteria, yeasts, moulds and other saprophytic microorganisms. Their populations tend to flourish in the presence of moulds since mites also feed on moulds and the moulds help to break down (pre-digest) and soften the skin scales.

For example, it has been suggested that the growth of the house dust mite, Dermatophagoides pteronyssimus, in carpets, mattresses and dust may be stimulated by growth of xerotolerant (drought-tolerant) species of Aspergillus such as Aspergillus glaucus on human skin scales and other dry household organic particulates.

However, with rising relative humidity (RH) mould activity increases rapidly and above 85% RH mite populations decline as the food supply becomes contaminated by mould and other microbial metabolites.

Moulds, Mites and Allergy

Moulds and mites allergens trigger allergic reactions in sensitive individuals. Mould spores are recognized allergens. Some of the allergies associated with mould exposure include:

• Immediate type hypersensitivity (Type 1 allergies).
• Delayed type hypersensitivity (Type 3 allergies) also referred to as allergic alveolitis. These types of allergies are characterized by wheeze, shortness of breath, cough, chest tightness, and in some prolonged cases, pulmonary fibrosis.
• Allergic bronchopulmonary aspergillosis (ABPA). In this case the bronchial passages are colonized by a species of Aspergillus, usually Aspergillus fumigatus, Aspergillus flavus or Aspergillus niger.
• Allergic mycotic sinusitis. This type of allergy involves infection of mucus adhering to the sinus walls.

The house dust mites (Dermatophagoides pteronyssinus, D. farinae, D. microceras, and Euroglyphus maynei) are the most important sources of allergens in house dust. At least 14 groups of allergens have been identified from D. farinae and D. pteronyssinus. These allergens have been implicated as causes of atopic asthma, perennial rhinitis, and atopic dermatitis among other allergic conditions.

Reducing the risk of Allergy and other respiratory problems

Reducing exposure to mould spores, mites and chemical pollutants reduces the risk of allergy and other respiratory problems. Since dampness encourages proliferation of moulds and mites and increases emission of chemical pollutants, reducing dampness in buildings would reduce exposure to these pollutants. Dampness in buildings can be reduced by:

• Mechanical ventilation.
• Vapour barriers.
• Channelling ground water away from foundations.
• Sealing below-ground walls.
• Protecting ground-level concrete slabs from moisture intrusion.
• Venting showers and other moisture-generating sources to the outside.
• Using air conditioners and de-humidifiers.
• Using exhaust fans whenever cooking, dishwashing, and cleaning.

Conclusion
Dampness in homes and workplaces should be controlled in order to reduce the risk of occupants developing respiratory problems.

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