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How to get rid of the millions of harmful ‘house guests’ – you can’t see

  • Researchers find up to one million mites in beds, plus mould and bacteria in house dust – all of which are bad for our health – but hi-tech help is at hand
  • Volatile organic compounds that leech in form of gases from household items such as air-fresheners, moth repellents, glue and marker pens also pose threat
PUBLISHED : Monday, 05 November, 2018, 10:02am
UPDATED : Monday, 05 November, 2018, 11:28am

You might not care to think about the hidden health hazards in your home.

Out of sight, out of mind, right? Unless itching, scratching, lethargy and headaches remind you that all might not be well.

When Dyson, the British household appliance company, decided to commission a random check of dust samples collected using its V6 cordless vacuum cleaners, the results were quite alarming.

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Analysis of dust taken from mattresses, furniture and floors in 33 Hong Kong homes by researchers from the Croucher Institute for Environmental Sciences at the city’s Baptist University revealed high concentrations of bacteria, mould and dust mites – all of which can exacerbate allergic reactions.

One million ‘unwanted’ house guests

Up to 46.7 mites were found in a single gram of dust, while the beds tested contained anywhere from 100,000 and 1 million dust mites each.

Most homes in the study also had above-average levels of mould present and exceeded the threshold that triggers allergic reactions; high levels can trigger rhinitis – inflammation of the inside of the nose – skin irritation, asthma or more serious, long-term respiratory and lung infections.

Keith Wong Ching-hai, manager at Johnson Group, a Hong Kong pest control company, says dust mites and mould are rightly the biggest concerns for householders.

A close third are the harmful volatile organic compounds (VOCs) that leech in the form of gases from countless items within the home, including paints, aerosol sprays, moth repellents, air-fresheners, dry-cleaned clothes, glue and marker pens.

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They can cause effects such as eye, nose and throat irritation, headaches, nausea, skin allergies and also cause damage to the kidneys, liver and central nervous system.

Many customers have experienced symptoms before they call in the professionals to investigate – but the good news is there is always a solution.

1. Dust mites

This microscopic malefactor sets up home in all your soft furnishings – mattresses, pillows, sofas and carpets – feeding on humans’ dead skin cells – yuck!

Hence, they particularly love your bed.

The worst part?

The itch that some people experience from dust mites is caused by their excretion.


Thijs Veyfeyken, general manager, European Bedding, says an organic latex mattress is the most mite-resistant as it is made from the sap of the rubber tree – an inhospitable environment for them to thrive in.

Opt for a mattress with a removable and washable cover, [which] like sheets can collect dust, mould and bacteria
Thijs Veyfeyken, general manager, European Bedding

In contrast, an innerspring mattress, with its many layers of padding and construction “is a breeding ground for dust mites”, he says.

“Opt also for a mattress that comes with a removable and washable cover.

“Just like your bedsheets, the mattress cover can collect dust, mould and bacteria.

“Periodically washing it will help reduce the amount of allergens that stay on your bed.”

He says people often ask him whether rubber is hot to sleep on.

“It’s what’s inside that counts,” he says.

Many “hybrid” mattresses are only part latex (the expensive part) with layers of foam or sponge that trap hot air inside, he says.

The company’s Heveya brand has seven zones with pin-core holes so the air can go in between all the layers.

“It can be slept on comfortably without the need for air conditioning,” he says.

Switching to hypoallergenic bedding may be helpful, too.

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Made from materials such as organic bamboo, silk, microfibre or high-quality cotton, sheet sets labelled hypoallergenic claim to repel dust mites and mould.

Dyson says that its V6 cordless vacuums remove fine dust, allergens and pollutants that often simply get pushed around by conventional sweeping and dusting.

A gadget available on Amazon, the Florious Living Bed Bug and Dust Mite Killer, purports to beat the bugs using ultrasonic wave technology, although not all the online reviews are favourable.

2. Mould

Living in humid places such as Hong Kong means you cannot escape the mould, mildew and fungi that sprout and thrive in such environments.

These micro-organisms can have damaging effects on the health.


Have the home professionally deep cleaned to remove any signs of mould.

Simply wiping it off won’t work, as the spores will remain.

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Johnson Group uses a chemical-free natural disinfectant – SmellGREEN – and can also test to find the name and nature of the fungus, which householders can then report to their doctor.

You can also consider applying an anti-mould coating, such as AerisGuard, or AURO anti-mould paint, to inhibit new growth.

If mould seems to be coming from within the concrete walls, make sure that leaky pipes aren’t the problem. If so, get them fixed.

Not all household fungus is visible – it can be found inside electrical appliances such as air conditioners and dehumidifiers, too.

Once detected, pest controllers can spray the inner workings with enzymes which break down and dissolve the layers, and will also enable your appliance to operate more efficiently.

Certain air purifiers also claim to have a mould-inhibiting function.

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For best results, consumers are advised to look for a model which has a true HEPA (high-efficiency particulate air) filter, as opposed to a “HEPA-type”, which can capture tiny particles as small as mould spores.

It should also be equipped with an ultra violet light (which actually kills mould spores) and an activated carbon filter that eliminates mould odour.

Models with HEPA filters include the HealthPro Series from the Swiss brand IQAir, while Hong Kong-based brand Oxyvital, made using German technology, meets World Health Organisation guidelines for all indoor air pollutant classes.

3. Formaldehyde

One of the most common VOCs, formaldehyde, is a cancer-causing chemical that occurs naturally in trees, fruits and vegetables. A small level is not harmful to health.

However, in urban areas, the levels build up because of smog and various pollutants, and it can be worse indoors where products containing man-made formaldehyde are common.

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Although we can avoid buying manufactured furniture that contains VOCs, many sources are invisible.

Formaldehyde is added to paints, coatings, plastic products, pesticides, cosmetics, mattress ticking – even, in some cases, air-fresheners and baby wipes.


Professional pest control companies have machines that can test for the level of VOCs and take remedial action if necessary.

Wong says this is particularly advisable following home renovations.

The process may include use of a fogging machine or misting fan to spray an eco-friendly, VOC-removing product onto wooden surfaces, then a fan to extract the toxins out.

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The next step is to open the windows to let the foul air out.

“We can never achieve zero emissions, but we can get them down to a safe level,” Wong says.

The use of an InovaAir E20 Plus air purifier – which has HEPA filtration – means the residual amount of formaldehyde or other VOCs will be decomposed gradually, he says.

Certain common indoor plants are also found to remove formaldehyde and other toxic agents from the air in the home.

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The most effective plant species, according to a study by the US American space agency, Nasa, in association with the Associated Landscape Contractors of America, include the rubber plant, aloe vera, Chinese evergreen, peace lily and spider plant.

4. Pet dander

We may love our furry friends, but not the hair they shed.


The Dyson Groom is a tool that can be attached to the brand’s vacuum cleaners to remove hair directly from your dog or cat, whisking it away before it escapes into the atmosphere.

Yet indoor pets shed at any time, so to keep the whole home relatively fur-free, a robotic vacuum cleaner can do a continuous clean-up while you are at work.

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Pet-oriented robot vacuum cleaners tend to have greater suction power and additional brushes to help sweep up stray hairs.

Some are equipped with HEPA filters to trap even the smallest dust and dirt particles.

In September Neato Robotics released two new “intelligent” robotic vacuum cleaners, the Botvac D4 and D6 Connected – sister models to the earlier D7 Connected – featuring LaserSmart mapping and navigation technology, including “No-Go” lines, so you can instruct the robot where not to go.

Another product, the Shark ION robot cleaning system, has a special attachment for pet hair and sofas, which can be linked with a cordless, handheld vacuum device for above floor cleaning.

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The Shark’s cleaning schedule may be programmed from anywhere via its companion app, or by using voice control through artificial intelligent-powered voice assistants, such as Amazon Alexa or Google Assistant.

How can future technology help?

However, in the future, technological advances may make many of these devices outdated.

We will use our expertise in plasma science … to ultimately produce a low-cost, efficient and effective technology that reduces the concentration of allergens from within the household environment
Dr James Walsh, University of Liverpool

Researchers at Britain’s University of Liverpool are developing an allergy relief device that uses technology linked to cold plasma – a form of ionised gas where energetic electrons and ions coexist alongside a wide variety of highly reactive chemical compounds – to tackle the problem of airborne allergens in the home.

They are following up on a recently discovery that when cold plasma comes into contact with contamination in the air, such as an allergy-causing fungus or household chemical, it has a very powerful sanitising effect.

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The technology requires only air and electricity to operate and typically uses 10 times less power than a household light bulb.

The researchers aim to develop a device that will be able to destroy the airborne allergens on contact.

Dr James Walsh, of the university’s department of electrical engineering and electronics, says: “This innovative research project has [a] real-life impact.

“We will use our expertise in plasma science … to ultimately produce a low-cost, efficient and effective technology that reduces the concentration of allergens from within the household environment.”