Sneezing throughout the day, itchy eyes, and a runny nose, those microscopic moulds are responsible for your ailments. This article deals with the description of common household moulds, the health hazards they cause, and what measures can be taken for prevention and treatment.

Introduction

Moulds are a kind of fungi that are present everywhere in the environment. They form filaments called hyphae as well as spores. They can enter your body via inhalation, ingestion of contaminated food, or through a breach in the skin and cause various allergies.⁶

You can experience allergic symptoms throughout the year as they enter your home through open doors and windows. Indoors, they can be found anywhere, growing on walls, furniture, floor tiles, bathrooms, carpets, trash cans, clothing, stored grains, and edible food products stored in improper conditions.^1,4 

Common household moulds

The common household moulds responsible for your ailments are:⁸

1. Yeast: is a fast-growing mould found everywhere and frequently infects humans worldwide. The colonies are smooth and white to cream coloured. Mostly, yeast infects the skin and gastrointestinal tracts, causing localised lesions. However, the infection can be disseminated in low immunity, leading to systemic mycoses
2. Mucor: colonies of Mucor are dark grey or light olive grey. Mucor is a rapidly growing mould predominantly found in buildings, stored food products, cattle manure, and hay. Mucor causes disseminated infection of the respiratory and central nervous system, paranasal sinuses, skin, and GI tract, called mucormycosis, in immunocompromised people
3. Penicillium: often grows inside damp buildings on wallpapers, carpets, and inside the duct insulation. The fungal colonies have a typical velvety, woolly, or cottony appearance. The colonies are white, green, yellow, or pinkish. Penicillium infects the skin, eyes, ears, and lungs in susceptible individuals
4. Rhizopus: the colonies are deep grey to black with a cottony appearance. This mould is often present on food items and in soil. In sensitive individuals, it causes coughing, wheezing, flu, and mucormycosis
5. Trichoderma: is frequently found outdoors in soil, decomposing plants, and paper. Indoors, it often grows on other fungi. The mould forms transparent white to green or yellow coloured colonies. Trichoderma causes allergies, infection of the sinuses, liver, lungs, skin, and brain abscess, mostly in immunocompromised and organ transplant people
6. Zygomycetes: is a fast-growing mould, commonly found in soil, decomposing plants, or animal bodies. Diabetes, prolonged steroid use, immunosuppressive therapies, low white blood cell count, broad-spectrum antibiotic use, severe malnutrition, and breach in the skin, such as by trauma, surgical wounds, needle stick injuries, and burns, predispose immunocompromised individuals to mould infections
7. Aspergillus: the colonies grow rapidly, are green, brown, or black, and have a woolly or cottony texture. Aspergillus thrives in soil, plant debris, compost, stored grains, wood, paper, dust, ventilation ducts, clothes, and carpets. It is the causative agent of asthma, lung oedema, bronchospasms, and lung emphysema. The aflatoxins produced by Aspergillus damage the liver and can cause p53 gene alterations
8. Cladosporium: is the most common slow-growing mould found in our houses, in dirty refrigerators, on moist window frames, paint, paper, clothing, and ventilation ducts. The colonies are olive-green to olive-brown in colour and have a powdery or velvety appearance. Cladosporium can cause infection of the lungs, eyes, skin, bones, and nails, mostly in immunosuppressed individuals
9. Chaetomium: produces cottony white, grey to olive coloured colonies on the damp walls. It causes infections of the skin, nails, lungs, and brain abscesses in susceptible people
10. Acremonium: produces loose cottony white, grey, or rose colonies. Its infection causes nausea, vomiting, and diarrhoea in immunocompromised people
11. Alternaria: infects the nose, mouth, and upper respiratory tract. It produces greyish white, greenish black, or olive brown colonies on carpets, clothing, and window frames
12. Arthrinium: flourishes on dead and decaying wood, leaves, litter, and organic matter. The colonies are woolly or cottony white with brown spots. It causes vomiting, nausea, diarrhoea, and encephalopathy, which can lead to coma and even death
13. Aureobasidium: grows in moist areas such as bathrooms, kitchens, on shower curtains, tiles, window sills, wet clothes, and liquid waste materials. The colonies are cream to pink coloured and later on become dark brown and velvety
14. Bipolaris: is a rapidly growing mould producing velvety to woolly white, greyish brown, olive green to black colonies. Bipolaris affects the eyes, skin, heart, bones, lungs, and brain
15. Curvularia: the colonies are white, pinkish grey, olive brown, or black. Curvularia is found in soil, plant debris, stored grains, and on wooden structures
16. Epicoccum: grows rapidly indoors and causes infection of the skin and lungs. It produces woolly, cottony, yellow, orange, red, pink, greenish brown, or black colonies
17. Fusarium: It produces white, tan, cream, yellow, salmon, cinnamon, pink, red, violet, or purple coloured colonies. Fusarium causes eye, skin, and nail infections
18. Paecilomyces: can grow in moist soil, dust, cosmetics, plastics, vinyl, and in edible food items. Paecilomyces infects the lungs, skin, heart, and sinuses
19. Torula: This mould forms dark brown to black velvety colonies. It grows on soils, dead wood, leaves, food, hay, textiles, and may cause hay fever and asthma
20. Stachybotrys: forms cottony white to dark green and black colonies. It grows rapidly on leaky walls, ceilings, and wallpaper
21. Scopulariopsis: forms white, light brown to tan coloured colonies. It is found on wallpaper, carpets, walls, cellulose boards, dust, shoes, and wood pulp. It may infect nails, lungs, soft tissues, bones, and rarely the eyes and ears, especially in immunocompromised individuals

Factors affecting the mould infestation

• Mould thrives in the presence of moisture. It could be due to leaks in roofs or walls, high indoor humidity, poor construction of houses, and poor maintenance²
• Poor ventilation of homes also leads to the accumulation of moisture on the walls, which contain different organic compounds that serve as a good nutrient source for moulds
• High humidity conditions develop more in wooden houses as compared to concrete houses¹
• The size of the spores of moulds determines their penetration into our airways. Spores of smaller size penetrate deeply into our respiratory tract

Allergic reactions caused by moulds

We are exposed to a variety of allergens daily. Normally, our bodies do not mount an immune response against those allergens, but some sensitive genetically predisposed people show unusual immune activity as sneezing, itching, swelling, rash, or respiratory issues. When an allergen enters our body, it produces antibodies called immunoglobulin E (IgE) in response. These antibodies stimulate the release of chemical mediators such as histamine, leading to allergy symptoms. Sometimes, these symptoms can be severe and life-threatening.³

Moulds can cause allergic rhinitis, conjunctivitis, bronchial asthma, allergic bronchopulmonary mycosis (ABPM), allergic fungal sinusitis (AFS), and hypersensitivity pneumonitis (HP) in adults. Children suffer from impaired memory, low IQ, and reduced cognitive abilities if they are exposed to a mould-infested environment on a long-term basis.^1,4

Moulds release mycotoxins, which cause allergies. If consumed in high doses, mycotoxins can cause acute poisoning, which may even result in death. Aflatoxin, produced by moulds, can cause irreversible liver damage, lung damage, neurological and neuropsychiatric symptoms, including pain, movement difficulty, delirium, dementia, imbalance, and incoordination. Even the mycotoxins can cause cancer.^6,7

Method of detection

It is crucial to determine the source and extent of mould growth to prevent adverse health effects of mould infestation. For this purpose, the samples are collected from homes as well as workplaces.⁷

 The various sampling techniques involved are:²

1. Air sampling: this technique involves capturing airborne mould spores and then comparing indoor samples with outdoor controls to evaluate airway exposure. This is useful to locate hidden mould sources
2. Surface and bulk sampling: using swabs or tapes, samples are collected from indoor surfaces. This helps identify mould species 

The airborne enzyme activity and volatile organic compounds emitted by moulds in the collected samples are measured by molecular techniques such as polymerase chain reaction (PCR), immunoassays, and gene sequencing.

The laboratory tests include the collection of:

• Urine
• Blood
• Faecal samples

The basic blood tests include:

• Analysis of electrolytes
• Blood sugar
• Liver function test
• Renal function tests

Specific blood tests are performed to measure the body's immunological response, such as:^2,7

• Detection of antibodies to moulds and mycotoxins in the serum
• Visual contrast sensitivity test
• Complement levels
• gamma globulin levels
• EEG of the brain
• Computed tomography (CT)
• Magnetic resonance imaging (MRI)
• Pulmonary function tests

These tests confirm the presence of moulds, determine their load, and identify their species. Unfortunately, there is no gold standard method for quantifying and identifying fungi. Combining different methods can help in diagnosis. Specialised equipment and expertise are required for the detection of moulds. The laboratory findings must be correlated with clinical symptoms and workplace/household exposure history before making a diagnosis of mould-related illnesses.^2,4

Treatment

Reducing exposure to the allergen is the optimal treatment for allergic symptoms. The aim is to keep the levels of moulds in the household/workplace to a minimum so that they don’t initiate an abnormal immune response. The allergies are treated symptomatically.³

1. Antihistaminics: drugs that prevent the release of histamine from mast cells, which is responsible for allergic symptoms
2. Steroids: drugs suppress the immune system 
3. Allergen immunotherapy: an approach that gradually increases doses of allergens given to susceptible persons to achieve immune tolerance. The person gets sensitised and experiences fewer allergic symptoms on subsequent exposures. This therapy is helpful to people who don’t achieve relief with medicines or develop side effects with medication 

Prevention

It is mandatory to control the growth of moulds in our living environment to protect our physical and mental health. This can be achieved by:^2,3,5

1. Controlling indoor moisture levels
2. Adequate household ventilation
3. Maintaining cleanliness
4. Use of air purifiers at home 
5. Repairing water leaks 
6. Educating people about moulds and allergic symptoms
7. By keeping the mould exposure to a minimum. The susceptible persons should avoid staying in damp/ leaky rooms until they are repaired 

Summary

Moulds are the microscopic fungi responsible for allergic symptoms such as itching, redness, sneezing, allergic rhinitis, allergic sinusitis, asthma, hay fever, and allergic bronchopulmonary mycosis in genetically predisposed persons. Humidity is a risk factor for mould growth on surfaces and leaky building walls. Controlling moisture levels, regular repair of damp walls, and usage of air purifiers can help reduce the proliferation of indoor moulds, improve respiratory health, and reduce the risk of allergic reactions.