A typical scenario: the whole house sneezing after the flood

(An illustrative example case, not a real family.)

Mali runs a grocery store in a two-storey shophouse in Nakhon Nayok town. The shop is downstairs, with a kitchen and the bedroom of her eight-year-old son, who has allergic rhinitis, at the back. While the water in town stayed high, the shop closed and the family carried what they could upstairs, but a fabric sofa, curtains, a spare mattress and cardboard cartons of stock stayed underwater for days.

When the water receded, they washed out the mud, dried the mattress in the sun, laundered the curtains and reopened within a few days. Everything looked fine, yet her son began sneezing every morning, with red eyes, an itchy nose and a night-time cough that kept him awake. Her husband had a blocked nose for the first time in his life. In the storeroom she found blue-green spots on the cartons, while the aluminium window frames and the rubber seal of the bathroom door were covered with olive-black specks. The bedroom air conditioner smelled musty every time it was switched on.

She was unsure whether her son's symptoms were linked to mold, what to throw away, and how to clean so the home would be safe for a child with allergies.

The 2026 flood in Nakhon Nayok town, as reported

This section uses only the facts in the cited reports and adds no figures they do not contain.

• Water in town: a Thairath headline reported that water in Nakhon Nayok town was still 40 to 50 cm high while outlying areas had begun to recede.
• Areas affected: Thai PBS reported on 30 September 2026 that 4 districts, 41 subdistricts and 397 villages in Nakhon Nayok province were affected, totalling 28,028 households.
• Water management: the Khun Dan Prakan Chon Dam was releasing water, according to Thai PBS.

These figures reflect the time of reporting and can change. Follow provincial, district and municipal announcements directly.

For mold, 40 to 50 cm of water in town may sound shallow compared with some areas, but it is high enough to soak sofas, mattresses on the floor, curtain hems, low wooden cabinets, cartons of stock and low power sockets in shophouses and houses. These are ideal food for Penicillium and Cladosporium, and with humid late-rainy-season air, mold can appear within days of the water going down.

What is Penicillium?

Penicillium is a genus of filamentous molds with several hundred species, found everywhere in soil, air and food. Many people know the name from penicillin, which was discovered from a mold in this genus, and from molds used in some cheeses. In a damp home, however, Penicillium is the mold that forms blue-green, grey-green or white-edged-green spots and patches on bread, fruit, walls, wallpaper, carpets, mattresses and cardboard.

Penicillium grows fast and needs less moisture than some black molds, so it is often among the first molds to appear after a flood. Its spores are small and light and detach easily when touched or blown by air, so they can be plentiful in indoor air. Penicillium also releases volatile organic compounds that produce the familiar earthy, old-room musty smell.

Worth knowing: Talaromyces marneffei, which was formerly classified as a Penicillium, is found in Southeast Asia, including Thailand, and causes serious infection in people with severely weakened immunity, such as those with advanced HIV. It is now placed in a separate genus from the household Penicillium molds discussed here. People with weakened immunity should ask their doctor about avoiding mold and soil exposure after floods.

What is Cladosporium?

Cladosporium is one of the most common outdoor airborne molds in the world, living on leaves, plant debris and soil. It is usually olive-green, brown or black, forming scattered small dots or soft, velvety patches. Indoors, Cladosporium favours surfaces where water vapour condenses: window sills and aluminium frames, bathroom grout and silicone, damp painted walls, curtains, and the fins and drain pans of air conditioners.

Cladosporium tolerates a wide range of temperatures and can grow in fairly cool places, such as areas in the flow of air-conditioned air or uncleaned refrigerators. Its spores are an important allergen, and airborne levels tend to rise during wet, humid periods. After a flood, a home receives spores both from outside and from mold growing on wet materials inside.

Neither Penicillium nor Cladosporium spreads from person to person. The problem comes from breathing in airborne spores and fragments, so reducing mold sources at home is the main form of prevention.

Where Penicillium and Cladosporium hide in homes and shophouses after a flood

• Mattresses and fabric sofas: foam and fibre hold a lot of water. Sun only dries the surface; the inside stays damp and feeds Penicillium.
• Curtains and carpets: hems that sat in water, and fabrics washed but not fully dried.
• Cardboard cartons and stock in storerooms: food for Penicillium, often stacked against walls in stuffy corners.
• Low wooden cabinets and shelves: swollen plywood and particle board, and the backs of cabinets against walls.
• Window sills, door frames and rubber seals: condensation points where Cladosporium forms black or olive dots.
• Bathrooms: grout, silicone and ceilings, already damp and even damper after a flood.
• Air conditioners: filters, cooling coils, drain pans and blower wheels. If a unit sat in a damp, closed room for days or its outdoor unit was flooded, have a technician check and clean it before use.
• Ground-floor masonry walls: they do not grow mold inside like gypsum, but slow drying leaves paint and surfaces hospitable to mold.
• Refrigerators and shop chillers: door seals and drip trays, especially in units that were off for days.

Signs to watch for include blue-green or olive-black spots, a musty smell that gets stronger when a room is shut, an air conditioner that smells when switched on, and family allergy symptoms that worsen at home but improve outside.

Allergy from Penicillium and Cladosporium: symptoms and who is at risk

For most people the main problem with these molds is not infection but allergy and airway irritation. When a mold-sensitive person inhales spores, the immune system overreacts, causing:

• Allergic rhinitis: bouts of sneezing, clear runny nose, congestion and itching, often worst in the morning or in stuffy, damp rooms.
• Allergic conjunctivitis: itchy, red, watery eyes.
• Asthma flare-ups: cough, chest tightness and wheezing, especially at night. The WHO concludes that indoor dampness and mold are associated with asthma exacerbation and respiratory symptoms in children and adults.
• Eczema flares: in people who already have atopic dermatitis.
• Hypersensitivity pneumonitis: uncommon, caused by repeated heavy exposure to moldy dust, with fever, cough and breathlessness a few hours after exposure.

People who need extra care include children with allergies or asthma, adults with asthma or COPD, older people, babies, pregnant women and people with weakened immunity. Household molds rarely cause infection, but these groups should avoid unnecessary exposure and should not clean moldy areas themselves.

A key fact many people do not know: dead mold spores and fragments can still cause allergies, because the proteins the body reacts to remain. In a home with allergy sufferers, disinfection alone is not enough; moldy materials must be removed and dust vacuumed with a fine enough filter.

Important: if a child or family member has allergy symptoms that do not improve, frequent asthma attacks, breathlessness, fever or a persistent cough, see a doctor and mention the flood and mold. Do not change or add medicines yourself. Anyone who waded through floodwater and then developed fever, calf pain or diarrhoea should see a doctor promptly, as this may be a flood-related infection such as leptospirosis. This article is not medical advice.

Why Penicillium and Cladosporium rise so fast after a town flood

Three things come together in a town like Nakhon Nayok once the water drops. First, there is a huge amount of wet, soft material at floor level: mattresses, sofas, curtains, cartons, wooden furniture and clothing. Second, the late rainy season keeps outdoor humidity high, so opening windows does not dry a room as quickly as people expect, and every evening brings condensation on cool glass and aluminium. Third, families are understandably eager to get back to normal life, so damp items are often put back in place before they are truly dry.

Penicillium takes advantage of the soft, absorbent items, while Cladosporium settles on the condensation points and in air conditioners. Because both produce light spores in very large numbers, a few moldy items in one corner can raise spore levels throughout a small shophouse. That is why the most effective response is not a single product but a sequence: remove the worst sources, dry what remains, clean surfaces, control humidity and then disinfect. Each step reduces the load that the next step has to deal with, and skipping one usually means the smell and the sneezing come back.

How allergy molds affect families and shops

Health and sleep: a child who sneezes and coughs all night sleeps badly and goes to school tired, while parents are up in the night too. The whole household wears down.

Hidden costs: doctor visits, medicine, repeated curtain washing and replacing furniture that grew mold after you tried to save it.

Damaged stock and reputation: moldy cartons and boxed goods cannot be sold and can spread mold through a storeroom, and customers who smell mustiness hesitate to buy food or household items.

Lost time: cleaning the wrong way lets mold return, and the work must be repeated when the shop should be trading again.

Why familiar fixes are not enough for allergy molds

Sun-drying a mattress and using it again: sun dries the outside, but foam that sat in floodwater for days stays damp inside and may be contaminated with sewage. CDC advice is to discard mattresses and cushions soaked by floodwater.

Dry sweeping and dusting: this sends spores into the air and triggers symptoms immediately in allergic people. Use a damp cloth or a HEPA-filter vacuum.

Turning on the air conditioning to dry the room: if the unit already has mold, it blows spores through the bedroom.

Using bleach on everything: it works on some hard surfaces after dirt has been washed off, but not on porous materials and fabric, and its fumes irritate asthmatic airways. Never mix it with ammonia or some toilet cleaners.

Incense or air freshener: smoke and fragrance can themselves trigger asthma, and they do nothing to reduce mold.

Disinfecting without removing moldy materials: dead spores still cause allergies, so disinfection must always follow removal, cleaning and drying.

WHD disinfection spraying: the final step for homes with allergy sufferers

World Health Disinfection (WHD) provides a disinfection spraying service for houses, shophouses, shops and buildings. According to the service information, trained technicians spray and/or apply an Ultra Low Volume (ULV) fine mist so the disinfectant coats floors, walls, window sills, shelving and frequently touched surfaces. WHD is based in Bangkok and takes bookings by phone or LINE; for provincial areas such as Nakhon Nayok, ask in advance when a team can travel.

The disinfectant is CHEMGENE HLD4H, a medical-grade product from the United Kingdom containing Benzalkonium Chloride and Didecyldimethylammonium Chloride. According to the product and service information it is broad-spectrum against viruses, bacteria and fungi; the service page states 99.99% efficacy, the product page 99.85% against COVID-19 within one minute, and the website cites the Thai Department of Medical Sciences, Mahidol University, NHS England and EN 14476:2013+A2:2019.

Being honest about efficacy: WHD's pages list COVID-19, Human Coronavirus 229E, RSV, influenza H1N1 and H5N1, HIV, norovirus, hand-foot-and-mouth virus, vaccinia virus, mycobacteria, Salmonella, Bordetella pertussis, bacteria in general and fungi, but give no specific test result for Penicillium or Cladosporium. We therefore do not claim kill figures for them. What can be said is that both belong to the fungi group the product states it covers, and that WHO and the CDC advise cleaning and then disinfecting flood-contaminated surfaces. For test data on a specific organism, ask WHD directly. Spraying does not remove the allergens in dead spores, so removing moldy materials and proper vacuuming are always necessary.

How the service works

1. Book by phone or LINE with your location, floor area and condition after cleaning.
2. Prepare: remove food, food stock, dishes, toys and personal items, and take pets and plants out.
3. Technicians spray or mist CHEMGENE HLD4H. Everyone, especially children and people with asthma, must leave the sprayed zone.
4. Wait for the technicians' re-entry time, about 30 minutes according to the service information, then use the space normally.
5. Ventilate, and wipe food-contact surfaces with clean water as advised.

According to the service information, WHD's clients range from residential buildings, schools and offices to hospitals and malls. Tax invoices are available, and a free CHEMGENE spray bottle and WELLGIENIC wet tissues come with the service. For bedrooms where mustiness lingers in the air, WHD's ozone disinfection service is a possible add-on, also carried out in an empty room.

10 reasons Nakhon Nayok homes and shops should book WHD

1. Mold is not the only problem: town floodwater brings drain bacteria, viruses and mold together. Disinfection spraying with a product stated to cover all three is better value.
2. Mist reaches window sills and shelf gaps: exactly where Cladosporium settles.
3. Spares allergic family members: high-risk people avoid contact with moldy dust and disinfectant.
4. Suits shops that must reopen fast: about 30 minutes before re-entry, according to the service information.
5. Medical-grade disinfectant: with standards and institutions cited in the product information.
6. Trained technicians: they close off areas and apply correctly.
7. For shophouses, houses and dormitories: sales floors, stockrooms, kitchens and bedrooms.
8. Can be combined with ozone: for rooms where musty air lingers.
9. Tax invoices: convenient for shops and businesses.
10. Customer confidence: tell customers the shop has been cleaned and professionally disinfected.

Before and after: a home that dealt with allergy molds properly

Example case: a house with an asthmatic child

(An illustrative example case to explain the order of work, not a real customer review.)

Tai's family lives in a single-storey house within Nakhon Nayok municipality, and their youngest daughter has asthma. After the water receded, they decided she should stay with relatives instead of coming straight home. Meanwhile, the adults wore N95 masks and gloves, threw out every soaked mattress, fabric sofa, carpet and cardboard box, washed floors and walls with water and detergent and ran dehumidifiers for several days.

A technician cleaned both air conditioners, the curtains were replaced and the bathroom grout was scrubbed. Then they booked WHD to spray the whole house. Everyone left during spraying, returned when the technicians said so and opened the windows. When their daughter came home, they kept watching her symptoms and kept her regular doctor's appointment.

What this case gets right: the child was kept away during clean-up, allergen sources were removed first, and spraying was the finishing step, not the first.

Checklist to reduce allergy molds before and after spraying

Before spraying

• Have children, older people and anyone with allergies or asthma stay elsewhere during clean-up.
• Wear an N95 mask, gloves and goggles when handling moldy items.
• Discard soaked mattresses, pillows, fabric sofas, carpets and cardboard.
• Wash curtains and salvageable fabrics in hot water where the fabric allows, and dry completely.
• Wash floors and hard surfaces with water and detergent; do not dry-sweep.
• Clean the air conditioning and replace filters.
• Run dehumidifiers or ventilate until the house is dry.
• Remove food, food stock, dishes and toys from the spray zone.

After spraying

• Wait for the technicians' re-entry time, then ventilate.
• Wipe food-contact surfaces and children's toys with clean water as advised.
• Keep humidity in check: the US EPA recommends indoor relative humidity below 60%, ideally between 30 and 50%.
• Clean air conditioner filters regularly and wipe condensation from window frames.
• Watch family allergy symptoms and see a doctor if they do not improve.

Frequently asked questions about Penicillium, Cladosporium and spraying

Q: How is household Penicillium related to the antibiotic penicillin?
A: Penicillin was discovered from a mold in this genus, but having Penicillium at home brings no benefit. Penicillin drug allergy and mold allergy are separate matters.

Q: Why are my child's allergies worse after the flood when the house looks clean?
A: Spores can be airborne without visible stains, coming from mattresses, air conditioners or behind furniture. See a doctor and look for mold sources at home.

Q: Does CHEMGENE HLD4H kill Penicillium and Cladosporium?
A: WHD's pages state it covers fungi but give no specific result for these two genera. Ask WHD directly for test documents.

Q: Will spraying make allergies disappear?
A: Do not expect that. Dead spores still cause allergies, so removing moldy materials, HEPA vacuuming and humidity control matter just as much, and allergy treatment belongs with your doctor.

Q: Do we have to leave during spraying?
A: Everyone must leave the sprayed zone and return at the technicians' stated time, about 30 minutes according to the service information. People with asthma should return after ventilation.

Q: Does WHD serve Nakhon Nayok?
A: WHD is based in Bangkok and books by phone or LINE. Ask in advance when the team can travel.

Q: Does the disinfectant leave residue?
A: We do not claim it leaves none. Wipe or rinse food-contact surfaces and toys with clean water as advised.

Make home a place where everyone can breathe easily

Once cleaning and drying are done, let the WHD team finish with CHEMGENE HLD4H disinfection spraying. Ask about details, documents and available dates through any channel.

Book Disinfection Spraying

Phone 065-556-6294 · LINE @whd268 · worldhealthdisinfection@gmail.com

Related links and references

Internal links

• WHD disinfection spraying service
• CHEMGENE HLD4H disinfectant
• Residential ozone disinfection
• Contact us

External references

• Thai PBS on the Nakhon Nayok flood, 30 September 2026: thaipbs.or.th/news/content/558912
• Thairath (headline) on 40 to 50 cm of water in Nakhon Nayok town
• CDC, Floods and mold after flooding: cdc.gov/floods
• WHO fact sheets and indoor air quality guidance: who.int/news-room/fact-sheets
• Department of Disease Control, Thailand: ddc.moph.go.th

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Keywords: Penicillium, Cladosporium, mold allergy, allergy mold after flood, post-flood disinfection, Nakhon Nayok flood 2026, disinfection spraying service, CHEMGENE HLD4H