Is the Mould in My House Causing Skin Rashes, Eczema, and Asthma?

However, if you already have mould in your home, you can try the following methods to remove it. The key is to clean the mould, reduce moisture, and prevent it from coming back.

Prepare:

• Bleach: Mix 1 part bleach with 3–10 parts water and scrub visible mould off the surface.
• Dehumidifier: Use a dehumidifier to keep indoor humidity between 40–60%.
• Fans / Ventilation: Keep the area well ventilated using fans or by opening windows

Some people use refillable moisture absorber kits,  where silica gel beads are placed in plastic containers around the house, especially in bathrooms. This helps absorb moisture after showering and prevents warm moisture from rising and condensing on the ceiling, which is where mould often grows (usually costs around SGD $20-$30).

You can check the product here.

Once the leak source is repaired (often via PU Injection or re-waterproofing above), repaint the ceiling with anti-mould or fungicide-laden paint. 

For mould on the wall:

Mould on walls usually means there is an ongoing moisture problem, so the first step is always to find and stop the source of the dampness. 

After that, the affected area needs to be cleaned thoroughly, any loose paint or plaster should be scraped away, and the surface should be sealed with a fungicidal or alkali-resistant sealer. 

Finally, repaint with anti-mould paint. If the wall feels soft or the mould keeps coming back, it may be necessary to remove part of the plaster to fully fix the issue.

For mould on ceiling:

Ceiling mould is more often caused by poor airflow and condensation rather than a hidden leak. Treatment therefore focuses on improving ventilation in the room. The mould area still needs to be cleaned and sealed, but once this is done and the humidity is controlled, ceiling mould is less likely to return. However, if humidity stays high or ventilation remains poor, the mould may come back.

Note: You might have seen “mould testing kits” going viral online. These can range from super cheap (around $10) or up to $1000 if you’re willing to pay for those high-grade air sampler systems. But the results may not be immediate.

“If there’s only seepage and no visible mould, can I just leave it alone?” 

Some people have reported feeling like there is mould even when nothing is visible. For example, a Reddit user @Additional-Flight777 shared that they suspected mould but could not see it. 

Another user @_TheBgrey also mentioned that a family member insisted there was mould because of the smell, even though nothing could be seen.

In situations like these, it is not safe to assume the problem is gone. Mould can grow hidden beneath paint or inside the ceiling structure, especially where damp patches are present. Even if the surface looks fine, the mould may still be developing underneath.

“Is grouting effective for blocking seepage?”

Grouting can be effective for small, localised leaks like hairline cracks by injecting resin to block water entry, without hacking finishes. This is why it’s commonly used in basements and structural works.

However, if the root cause is poor water management such as blocked drains, bad slope, or ponding water, grouting only shifts the problem to another weak point. In these cases, it treats the symptom, not the cause.

Good practice starts with controlling the water first by clearing drains, checking downpipes, and ensuring proper water flow away from the building. This applies to all building types, including landed homes, condos, and HDB flats.

“I think there is mildew rather than mould growing on my ceiling. How should I handle it?”

Mildew is usually a surface-level growth caused by poor ventilation and condensation, especially on ceilings. It often appears light grey or whitish and does not penetrate deeply into the plaster.

In these cases, the priority is improving airflow. Using an exhaust fan or opening windows regularly helps reduce trapped moisture. The affected area can then be gently wiped with diluted vinegar or mild detergent and water, and allowed to dry completely. 

Once the surface is clean and dry, repainting with an anti-mould or anti-fungal interior paint is usually enough. There is no need to hack the plaster as long as it remains firm.

“Is this just dry plaster flaking off, or a seepage issue I should be worried about?”

In the first photo showing ceiling bumps, the raised, blister-like areas are most consistent with moisture-related paint blistering. This usually happens when water vapour or past seepage becomes trapped beneath the paint film, causing it to swell and lift.

Common sources include an old roof leak, bathroom moisture from the unit above, or condensation over time. Even if the area feels dry now, the damage pattern suggests there was previous moisture exposure. A normal internal repaint alone will not solve this issue.

For this situation, you can try the following:

1. Identify the source of the seepage and report it to HDB or the condominium management, if possible
2. Scrape off the bubbled paint
3. Apply a stain-blocking sealer
4. Finish with repainting using a suitable interior paint

In the second and third photos, the long lines and flaky areas are typical of hairline concrete or plaster cracks combined with paint delamination. This is very common in concrete buildings and often results from structural movement, thermal expansion, or the failure of old repairs. The flaking occurs because the paint has lost adhesion to the plaster underneath.

Although these areas may look “dry,” dry plaster flaking does not mean there is no mould. Mould growth depends on whether moisture was present in the past, not whether the surface is dry at the moment. Previous moisture damage can still leave spores behind.

For these flaking and cracked areas, applying a new coat of paint alone is only a cosmetic, short-term fix. A more sensible approach is to scrape off all loose paint, fill the cracks with a flexible crack filler, seal the surface with an alkali-resistant sealer, and then repaint using a good-quality interior paint, preferably one with anti-mould properties.

This method improves paint adhesion and helps prevent stains or peeling from returning too quickly. Without proper sealing, repainting usually fails again within months.

“Do mould mites come with wall mould?”

If you have mould on your wall, there is a possibility that mould mites are present, but it is not guaranteed. Mould mites are tiny and feed on mould spores. They usually appear only when mould has been present for a long time and moisture levels remain high.

They are difficult to see without magnification, but some people notice indirect signs such as increased allergic symptoms, itchy skin, or tiny white or beige specks moving slowly on mouldy surfaces. Fresh or dry mould does not always attract mites, but persistent damp mould increases the likelihood.

When mould in the home is left untreated, especially in damp environments, it can progress into what many people fear most: black mould. This is where health effects, including skin flare-ups, become more likely.

The term “black mould” sounds alarming, but it is actually the common name for a specific species of mould called Stachybotrys chartarum. To clarify, all moulds are fungi, but not all fungi are moulds.

Stachybotrys chartarum is commonly found in damp indoor environments, particularly in buildings with water damage. A study examining water-damaged building materials found that several fungal genera were frequently present, including Penicillium (68%), Aspergillus (56%), Chaetomium (22%), Ulocladium (21%), Stachybotrys (19%), and Cladosporium (15%). All of these are known to trigger respiratory allergies, and among them, Stachybotrys chartarum was one of the most commonly detected species.

What makes Stachybotrys chartarum particularly concerning is its ability to produce potent airborne mycotoxins. These toxins have been linked to severe respiratory problems, immune suppression, and, in rare and extreme cases, pulmonary hemorrhage.

People are very cautious about this issue. For example, a Reddit user @peepeepoopoofoot who was renting a house recently moved a small dresser in his closet and discovered a large amount of black mold at the bottom. He became worried because he had spent a lot of time in that room with his cat. Should you be concerned too?

Well, the previous research does not conclusively prove that it is more dangerous than other toxic moulds such as Aspergillus or Fusarium. The risk depends largely on the level and duration of exposure.

Importantly, it highlights that inhalation of mycotoxins is significantly more dangerous than skin contact or ingestion. This is due to what scientists call greater fungal bioavailability through the lungs. The alveoli, or air sacs in the lungs, have an extremely large surface area, very thin barriers, and a dense blood supply. 

When mycotoxin-containing spores or fragments reach this region, the toxins can pass directly into the bloodstream with minimal resistance, increasing their potential impact on the body.

For people with asthma, the response is more pronounced. Asthmatic airways are already inflamed and sensitive, so mould particles can trigger stronger immune reactions. This leads to airway narrowing, increased mucus, and swelling, which can make breathing feel tight or difficult. Even low-level exposure can worsen asthma symptoms, and repeated exposure can reduce overall asthma control.

For people with eczema, the black mould rash is linked to immune sensitivity and a weaker skin barrier. Although mould exposure happens through breathing, mould particles can still activate the immune system throughout the body. This can increase inflammation signals that affect the skin, making itching and redness worse and triggering flare-ups, especially in damp environments.

When a healthy person breathes in particles from black mould, skin rash from mold exposure usually happens through tiny spores or fragments floating in the air, not because the mould is infecting the body. These particles can settle in the nose and airways, and some are small enough to reach the deeper parts of the lungs called the alveoli.

The body’s immune system is built to recognise foreign particles like these. Components of mould, such as beta-glucans and enzymes, trigger a short-term immune response. This causes mild inflammation that helps the body trap, break down, and remove the particles. In most healthy people, this process is effective and settles on its own without causing long-term damage.

Some types of black mould can produce toxins called mycotoxins. When present, these can place extra stress on cells. However, in typical home environments, the levels are usually low. The lungs, liver, and immune system are generally able to process and clear these substances. As a result, symptoms in healthy individuals are usually mild and temporary, such as throat irritation, nasal congestion, or coughing.

Many people assume that any mould that looks black is dangerous, but this is a common misconception. Mould color alone does not determine whether it is toxic or harmful.

Black-Colored Mould

Black-colored mould refers to any mould that appears black or very dark. Many mould species can look black due to their age, environment, or the surface they grow on. Most of these moulds are common indoors and outdoors and are not considered toxic, although they may still cause allergies or irritation in some people.

Black Toxic Mould

Black toxic mould usually refers to specific mould species that can produce mycotoxins, most commonly Stachybotrys chartarum. These toxins are not always present; they are produced only under certain conditions, such as prolonged moisture. Because of this, even toxic mould is not always harmful in every situation, but it does require more caution.

Here’s the comparison:

Is it Mould or Dirt?

@cappyMTL from Reddit shared this and wasn’t sure whether it was mould or dirt.

From the photo, this looks more like a mix of dirt and a bit of mild mildew rather than black toxic mould. Window tracks are spots where dust, outdoor debris, and moisture naturally build up over time, especially because condensation often forms there and airflow is limited. The dark marks look scattered and dry, not thick or slimy, which usually points to everyday grime instead of serious mould growth.

It’s also worth noting that toxic black mould tends to grow in places that stay damp for long periods and usually forms darker, heavier patches on materials like drywall or wood. In this case, the surface looks like a window frame, where dirt and light mildew are very common. A simple clean with soap and water or vinegar, followed by drying the area well, should take care of it.

Another case. Looking at this photo by Reddit user @RecognitionOk8628, this does look like mold (or mildew) on the leather, not just dirt.

The giveaway is the light grayish-white, spotty pattern spread across the surface. Dirt usually looks darker, smeared, or concentrated in high-touch areas. Here, the spots look more powdery and uneven, and they’re appearing in clusters, which is very typical of mold growing on leather. Leather is especially prone to this when it’s stored in a humid, poorly ventilated place, because it’s an organic material that mold can feed on.

This kind of mold on leather is usually surface-level and common on bags, shoes, or jackets that haven’t been aired out for a while. It doesn’t automatically mean anything dangerous, but it does mean the bag needs attention. If left untreated, mold can damage the leather over time and keep coming back.

Why is Black Mold So Common Indoors and Not Outdoors?

As asked by Reddit user @Careful-Training-761, the short answer is that black mold finds it much easier to survive indoors. Inside a home, moisture from leaks, condensation, or poor ventilation can stick around for a long time. When damp areas don’t fully dry, mold has the chance to grow. On top of that, common indoor materials like drywall, wood, and fabric give mold plenty to feed on.

Outdoors, things are less predictable. Surfaces dry faster, sunlight helps break mold down, and constant airflow makes it harder for mold to settle in one place. Even though mold spores are everywhere, indoor spaces provide the steady moisture and shelter that black mold needs to thrive.

Black Mould During Pregnancy: Is It Super Dangerous?

User @Bratislava30 was 28 weeks pregnant when she found black mould in her house. Is it super dangerous for her and her baby? The short answer is that it’s usually not super dangerous, even at 28 weeks pregnant.

There’s no strong evidence that normal household mould exposure directly harms the baby. Most concerns are related to irritation for the mother, such as coughing, congestion, or headaches, rather than pregnancy complications. Brief or past exposure is very common and not considered an emergency.

The important thing is to limit ongoing exposure. Clean or avoid the mould if possible, and if you experience persistent symptoms or are dealing with a large mould problem, it’s a good idea to mention it to your OB for peace of mind!

Is Black Mould Same as Sick Building Syndrome?

Many people often associate black mold with “sick building syndrome,” similar to what Reddit user @catgirlfriendd shared in her thread titled “So like, how serious is mold/other causes of being sick?”. 

The post explains that molds (and mildew) are among the leading causes of sick building syndrome, with symptoms ranging from mild to severe depending on the amount of mold present and an individual’s susceptibility.

Can I clean it myself?

Yes, you can clean mould yourself if it is small, localised, and on accessible surfaces, as long as you take proper precautions.

Start by removing visible mould using a non-toxic cleaner or Concrobium. Gently scrub the affected area and allow it to dry completely. Always wear gloves, a mask, and eye protection to reduce exposure to spores and cleaning residues.

Fixing the moisture source is essential. If the wall or ceiling remains damp, mould will return regardless of how well you clean it. Disinfectants help reduce surface contamination, while products like Concrobium can help inhibit regrowth.

DIY cleaning is usually safe and effective for small patches. However, for large infestations, recurring mould, or mould growing inside walls or ceilings, professional remediation is strongly recommended.

Do I need stronger chemicals?

No. Safe mould removal focuses on physical removal and moisture control, not on using stronger or more concentrated chemicals. For most surfaces, mild cleaning solutions work well, such as:

• Detergent and water
• 70% isopropyl alcohol
• 3% hydrogen peroxide

For non-porous surfaces like tiles, glass, or cabinets, commercial anti-mould sprays can be used safely.

For porous materials such as concrete walls, gypsum boards, or skimming layers, chemicals alone will not reach mould growing within the material. In these cases, the proper approach is to scrape off or remove affected sections, dry the area thoroughly, then seal or repaint.

Using stronger chemicals does not guarantee better results. In fact, it can increase irritation, especially for people with asthma or eczema. Concentrated bleach or quaternary ammonium compounds can leave behind volatile residues even after surfaces appear dry. These residues can release fumes or microscopic particles that irritate the respiratory tract.

For asthma sufferers, this can trigger coughing, wheezing, or shortness of breath even when mould is no longer present. For eczema or sensitive skin, chemical residues can disrupt the skin barrier or trigger immune reactions, leading to redness, itching, and flare-ups. In short, stronger chemicals can increase health risks without improving mould removal.

Which services in Singapore specialise in black mould treatment?

If professional help is needed, these companies are commonly used in Singapore:

The Mold Fix

• It offers up to a 2-year warranty, one of the longest reported in Singapore, so we recommend it.
• Timeline depends on scope
  • Entire 5-room HDB flat: approximately 2 to 3 days
  • Single room ceiling: approximately 2 to 3 hours

Mouldgone (under Rentokil)

• 6-month warranty
• Specialises in mould mite treatment
• Sells Concrobium cleaner (around SGD 148.90 for 3.7 litres / 1 gallon)

Ridpest Pte Ltd

• Free inspection services
• 24/7 same-day service available

After cleaning mould from your wall or ceiling, you may wonder how long it takes to know if the problem is truly solved.

Generally, if you stay symptom-free for about six months, meaning no itching, no sneezing, and no respiratory irritation, it usually means the wall or ceiling is no longer affected by mould.

However, if symptoms return within 2 to 3 weeks after mould removal and repainting, it usually indicates that the moisture problem is still there. In older homes or HDB flats, common causes include leaky air-conditioning systems, aging water pipes, or persistent condensation, which allow mould to regrow even after cleaning.

We believe the most effective way to restore your skin after mould exposure is to address the root cause, including environmental factors that may be affecting your health. 

Next, focus on calming and repairing the skin barrier. Gentle skincare, avoiding harsh products, and keeping the skin well-moisturised can help reduce irritation and support recovery.

Finally, personalised treatment is often needed when symptoms persist. If black mould in your home has contributed to your skin condition, it is important to assess both the trigger and the current state of your skin.

At Chinese Doc, we carefully evaluate your skin condition and create a personalised treatment plan tailored to your needs, helping to soothe irritation, support skin recovery, and restore overall balance.