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All about Mould Allergies

Last updated on 20th December 2023

Mould is spelled ‘mold’ in the US, and there are thousands of types of mould. They can grow indoors, for example in damp bathrooms and kitchens, and outdoors, for example in compost or in a garden shed.

Mould is a microscopic fungus made up of clusters of fibres. It reproduces via the production of small spores. These spores can be compared to the seeds of a plant, though they are much smaller than seeds or even pollen grains. Their small size makes them easy to disperse via wind and water. They can also travel long distances by clinging on to clothing or fur.

Mould is usually produced in damp and humid conditions as all types of mould need moisture to grow. Mould will grow in places with a lot of moisture, such as around leaks in roofs, windows or pipes, or where there has been flooding. Mould grows on materials that it can digest and use to spread; consequently, it may grow on any organic material.

It grows well on paper products, cardboard, ceiling tiles and wood products. Mould can also grow in dust, paints, wallpaper, insulation, drywall, carpet, fabric and upholstery. Mould in the air outside can also attach itself to clothing, shoes and pets, and can be carried indoors.

Since mould eats the materials it grows on, those materials end up damaged or degraded. Unchecked mould can cause cosmetic damage and staining, unpleasant odours, and even structural degradation of the surfaces. Mould digests the carbon in the surface it is growing on. While doing this, it breaks down the material bit by bit.

Uswitch asked 2,000 British adults 20 questions relating to mould in the home. Their research has revealed that almost two thirds (62%) of people claim to have had an issue with mould in their home at least once, with conditions in the home the most common reason for the spread of mould. 46% of people questioned struggled to pay their heating bills and may have not been able to keep their home adequately warm to prevent the mould.

Other reasons identified in the survey for mould growth included:

  • 40% of those who’ve had mould dried their clothes indoors.
  • 11% confessed to keeping the shower curtain folded when wet.
  • 22% left the kitchen or bathroom door open when cooking or showering.
  • 12% admitted to having a cluttered home.
  • 39.1% of people stated that they have been financially impacted by mould as cleaning and removing mould is expensive.

However, home maintenance is the primary reason for mould.

Here are some of the common areas where mould is found and their causes:


This is one of the most common reasons mould occurs. That is why mould is primarily found in kitchens and bathrooms where steam often appears from showering and cooking, resulting in more humid conditions than in other rooms.


This is another major cause of mould. Condensation is usually caused when warm air collides with cold surfaces. The moisture in the air cannot escape, resulting in mould. Therefore, you will notice mould on hard and cold surfaces such as tiles or around your windows.

Rising damp

This may indicate a serious issue in your internal wall. The issues related to rising damp could be due to plumbing leaks such as in the water pipes behind your walls or under your shower or bath.

Poor ventilation

Mould will develop without proper ventilation due to the build-up of condensation from everyday activities such as drying clothes indoors, cooking and showering, which can add moisture to the air.

Mould comes in different forms, some blackish and patchy, others green and textured. Knowing where mould grows in the home can help you stop the issue at its source and prevent you from continually trying to get rid of it.

Aside from the damage that mould causes on surfaces, there are health risks associated with exposure to mould; these health risks can range from mild to severe. These include the onset of mould/fungal allergy, respiratory infections, and the worsening of illnesses such as asthma.

Condensation can cause mould resulting in allergies

What is a mould allergy?

For some people, the spores that moulds release into the air can cause allergic reactions, although not all symptoms triggered by dampness and mould are allergy related. An allergy is the response of the body’s immune system to normally harmless substances such as mould.

Anyone can develop a mould allergy. However, some people are more sensitive than others. This includes elderly people, those with other allergies, people with existing skin problems, such as eczema, those who suffer from asthma, and people with a weakened immune system. Babies and children may be potentially at risk of increasing their chances of developing asthma or long-term allergies if they experience early exposure to mould.

Whilst in most people these substances or allergens pose no problem, in allergic individuals their immune system identifies them as a threat and produces an inappropriate response. This can be relatively minor, such as localised itching, but in more severe cases it can cause anaphylaxis, a condition which can lead to upper respiratory obstruction and collapse and can be fatal.

What are the types of mould allergies?

Several well-known conditions, such as Farmer’s lung and Sauna-taker’s lung, are caused by mould allergy. Mould spores can also lead to inflammation of the lungs, known as hypersensitivity pneumonitis. This is an immune system disorder which is triggered by an allergic reaction to inhaled dust and other substances such as mould.

In rare cases, people who have a long-term lung condition may develop aspergillosis which is caused by breathing in Aspergillus mould.

These conditions include:

  • Asthma.
  • Cystic fibrosis.
  • Bronchiectasis.
  • Sarcoidosis.
  • Chronic obstructive pulmonary disease (COPD).
  • A weakened immune system, for example, if you have had chemotherapy or an organ transplant.
  • Lung tuberculosis (TB).
  • Previous severe flu or coronavirus that was treated with mechanical ventilation (a breathing machine).

In exceptional cases, an individual may suffer a severe allergic reaction that may cause an anaphylactic shock. Anaphylaxis is the result of the immune system, the body’s natural defence system, overreacting to a trigger.

Anaphylaxis is a life-threatening, severe allergic reaction and is a medical emergency that requires immediate treatment. It must be treated with an Adrenaline Auto-Injector (AAI).

What causes a mould allergy?

Moulds release spores and it is these spores that cause the allergic reactions in some people. Most reactions to mould allergies aren’t serious and will be similar to that of hay fever or a sinus infection. The allergen isn’t the mould itself; instead, it is the spores released by the mould when the temperature in a damp environment rapidly increases.

An example of this is switching on the heating in a damp house. Reports of sudden asthma attacks during thunderstorms can be accounted for by a release of mould spores triggered by the storm.

There are some common types of mould in the home and health implications to look out for.

These are:


This mould, a type of fungus, causes aspergillosis. It is very common both indoors and outdoors, so most people breathe in these fungal spores every day. It is probably impossible to completely avoid breathing in some Aspergillus spores. There are approximately 180 species of Aspergillus, but fewer than 40 of them are known to cause infections in humans.

There are health hazards associated with Aspergillus. For people with healthy immune systems, breathing in Aspergillus isn’t harmful. However, for people who have weakened immune systems, breathing in Aspergillus spores can cause an infection in the lungs or sinuses which can spread to other parts of the body.


This tends to be velvet-like in texture with dark green or brown hairs. This type of mould tends to be found in damp places such as showers, baths, or under leaky sinks. It grows all year round but is most common between July and September. As it spreads quickly, it is a good idea to get rid of it as soon as you have spotted it. Health hazards associated with Alternaria can cause asthma-like symptoms affecting the upper respiratory tract, nose and mouth.


This begins as a pink, brown or black colour and usually turns a darker brown as it ages. It is one of the most common types of mould on walls and can often grow behind wallpaper or on painted or wooden surfaces. Health hazards associated with Aureobasidium can cause eye, skin and nail infections and it should never be touched with bare skin.


This is a greenish-brown coloured mould with a suede-like texture. It can grow in both cold and warm climates. It is often found in indoor materials, such as upholsteries, fabrics and carpets, and it can grow inside cupboards and under floorboards.

Health hazards associated with Cladosporium can cause allergic reactions to the eyes, nose, throat and skin and exacerbate asthma symptoms and sinusitis. Due to its potential for causing skin and lung irritation, Cladosporium should never be handled directly.


This is blue or green with a velvety texture. It can be found on spoiled food and common materials like wood, carpets, wallpapers and mattresses. It can be found throughout the year, with growth peaking between January and February. Health hazards associated with Penicillium are that the spores can become airborne and be inhaled by home occupants, leading to asthma and sinusitis.

It can harm those with weakened immune systems as it can worsen their symptoms and result in further health problems.

Black mould (Stachybotrys)

This is usually dark green or black and has a slimy texture that is easy to mistake for dirt. Humidity and damp conditions are the main culprits of black mould. This type is among the most common type of mould on windowsills as it grows in damp areas with high humidity levels, such as bathroom windows.

You will also spot black mould on natural materials such as wood, aluminium, wicker and paper. Health hazards associated with black mould are few as it is generally harmless, but those exposed to a specific strain called Stachybotrys may experience burning sensations in the airways, nose bleeds, fatigue, sinusitis, fever, headaches and a persistent cough. Stachybotrys is especially dangerous to children.

Aureobasidium mould in the home

What are the signs and symptoms of a mould allergy?

Symptoms of mould allergy vary from person to person.

The mould spores contact skin and nasal and bronchial membranes, causing symptoms such as:

  • Allergic rhinitis – This is where your nose gets irritated by something that you are allergic to. Common symptoms of allergic rhinitis are similar to a cold and include sneezing, an itchy nose, and a runny or blocked nose.
  • Itchy eyes and/or red and watery eyes.
  • A cough and/or the roof of your mouth being itchy.
  • Eczema – This causes the skin to become itchy, blistered, dry and cracked. Lighter skin can become red, and darker skin can become dark brown, purple or grey. Symptoms can affect any part of the body but most commonly the hands and face.
  • Asthma – This is a common lung condition that causes occasional breathing difficulties. The main symptoms of asthma are a whistling sound when breathing known as wheezing, breathlessness, a tight chest, which may feel like a band is tightening around it, and coughing.

Usually these symptoms happen within minutes of coming into contact with something that you are allergic to such as mould.

Symptoms of aspergillosis include:

  • Shortness of breath.
  • A cough – Which may bring up blood or mucus which can become very thick.
  • A wheeze – A whistling sound when breathing.
  • A high temperature of 38°C or above.
  • Diarrhoea.
  • Feeling or being sick.
  • Weight loss.
  • Fatigue – Feeling tired or weak.

The most severe allergic reaction is anaphylaxis. Although it is rare, it usually develops suddenly, and gets worse very quickly.

Any or all of the following symptoms may be present during an anaphylactic reaction:

  • Swelling of the tongue and/or throat.
  • Difficulty in swallowing or speaking.
  • Vocal changes (hoarse voice).
  • Wheezing or persistent cough or severe asthma.
  • Difficult or noisy breathing.
  • Stomach cramps or vomiting after an insect sting.
  • Dizziness, collapse or loss of consciousness due to a drop in blood pressure.
  • Floppiness in babies.

There may also be other allergy symptoms with anaphylaxis, including an itchy, raised rash (hives); feeling or being sick; swelling (angioedema); or stomach pain.

How is a mould allergy diagnosed?

If you think you or your child may have an allergy to mould your first port of call should be your GP who will arrange some allergy tests or refer you to a specialist allergy clinic to have them.

Tests you may have include:

  • A skin prick or patch test – This is where a small amount of the allergen is put on your skin to see if it reacts.
  • Blood tests – This is to check for allergens that may be causing your symptoms.

To test for aspergillosis your GP may arrange for a sample of mucus to be tested or for X-rays and scans or for a bronchoscopy where a thin, flexible tube with a camera at the end is used to look inside your lungs.

How is a mould allergy treated?

For mild allergic reactions, your doctor may recommend or prescribe medication such as:

  • Antihistamines – These are medicines often used to relieve symptoms of allergies. Most antihistamines can be bought from pharmacies and shops, but some are only available on prescription. They come in several different forms including tablets, capsules, liquids, syrups, creams, lotions, gels, eye drops and nasal sprays.
  • Steroid tablets – These are also called corticosteroid tablets; they are a type of anti-inflammatory medicine used to treat a range of conditions. Steroid tablets are only available on prescription. They are available in tablet, dissolvable, liquid and syrup versions.
  • Topical corticosteroids – These are a type of steroid medicine applied directly to the skin to reduce inflammation and irritation. Topical corticosteroids are available in several different forms, including creams, lotions, gels, mousses, ointments, tapes and bandages.
  • Reliever inhalers – These are prescribed for those who suffer from asthma. This provides quick relief when symptoms come on. The reliever inhaler works quickly to relax the muscles in the airways so that breathing is made easier.
  • Desensitisation (immunotherapy) for severe allergic reactions – This involves carefully exposing you to the thing that you are allergic to over time, so your body gradually gets used to it and does not react so badly. This should only be done by a medical professional.
  • Adrenaline auto-injectors (AAI), such as an EpiPen, will be prescribed for severe allergic reactions, such as anaphylaxis.

If you or someone you are with is having a serious allergic reaction and is showing signs of anaphylaxis, if they have an adrenaline auto-injector (AAI) such as an EpiPen, you should use it immediately as the allergic reaction may be life-threatening. Instructions are included on the side of the injector if you forget how to use it, or if someone else needs to give you the injection.

Call 999 for an ambulance after using the injector, even if you or the person you are with seem to be feeling better. If the person does not have an AAI, call 999 immediately and mention that you think the person has anaphylaxis; paramedics carry auto-injectors and will be able to administer adrenaline to control the reaction.

Aspergillosis is usually caused by inhaling tiny bits of mould but is rare in healthy people.

Treatment for aspergillosis depends on the type, and treatment usually helps control the symptoms, which include:

  • Allergic bronchopulmonary aspergillosis (ABPA) – An allergy to Aspergillus mould is treated with steroid tablets and antifungal tablets for a few months or possibly longer.
  • Chronic pulmonary aspergillosis (CPA) – A long-term lung infection is treated with long-term, possibly lifelong, treatment with antifungal tablets.
  • Aspergilloma – A ball of mould in the lungs, often linked to CPA, is treated by surgery to remove the ball if it is causing symptoms, often after antifungal treatment.
  • Invasive pulmonary aspergillus (IPA) – A life-threatening infection in people with a weakened immune system is treated with antifungal medicine given directly into a vein in hospital.

How to manage a mould allergy – asthma

There are numerous environmental factors and things that we encounter in our day-to-day lives that can trigger asthma symptoms or even an asthma attack; mould is one of these.

Everyone with asthma needs to use an inhaler, of which there are many types containing measured doses of different medications. The two main types of inhalers are called preventers and relievers. There are also combination inhalers which contain both a long-acting reliever and a steroid preventer.

Suffering symptoms of allergy

Preventing and dealing with mould

Avoidance whenever possible is the main treatment for dealing with allergies. Dealing with mould or preventing it in the first place, can reduce a person’s exposure to mould. There are steps that you can take for the prevention and irradiation of mould, and here are some practical suggestions.

Keep your home dry and well ventilated. Open windows regularly and have extractor fans in the bathroom and kitchen. If your home is prone to damp, you may want to buy a dehumidifier, which will collect moisture from the air.

You can also prevent the spread of damp air throughout the home by keeping doors closed when you are showering and cooking. If your double glazing does not have trickle vents, consider having these fitted.

Declutter – Mould likes stagnancy, a lack of airflow and moisture. The more things you have lying around, the more habitats are created for mould to thrive. Avoid drying clothes indoors wherever possible. Straighten out a wet shower curtain. Ensure anything damp is hanging and unfolded.

Allergy bedding covers protect you from mould spores within the mattress, pillows and duvets. Using filter facemasks, such as those worn by cyclists, traps spores and prevents you from inhaling them.

Be aware of other possible sources of mould. These include indoor plants, especially the material in the container that they grow in. Wear a dust mask if you are digging in the soil, cutting grass, or collecting decaying leaves, as wearing a mask can help prevent you from breathing in mould spores. Limit your time outside during damp weather or in areas with damp conditions such as woodland.

Sometimes you can do all of the above to prevent mould, but it will just slowly creep in. As mouldy spores begin to spread across walls and ceilings, it is natural to want to use the strongest cleaning chemical available, bleach. However, bleach simply takes the colour out of the mould leaving you to believe that it has gone, when in fact the fungus is still there.

Some alternative tips for cleaning and removing mould include:

  • It is essential to wear protective clothing while dealing with mould – Put rubber gloves on, and use safety goggles and a dusk mask before you start the process.
  • Use mould and mildew cleaning sprays.
  • Use white vinegar – Vinegar is acidic and slowly breaks down the structure of mould and kills it.
  • Use baking soda – Baking soda has a high pH that inhibits the growth and survival of mould.
  • Use a sponge to wipe the mould away.
  • For tighter spaces you can use a toothbrush for trapped mould.
  • To get rid of mould on walls and ceilings, you will usually need a paint scraper to remove the paint barrier and access the mould to remove it. Once paint or wallpaper is scrapped off, use mould removal spray and a firm sponge to remove the mould.
  • Don’t paint over mould, it will just continue to grow.

To prevent mould from growing and worsening in your home, it is crucial to recognise and remove the fungus as soon as possible. To stop mould and mildew from ever coming back, it is essential to get to the root of the cause of the damp in your home and take proper precautions. Mould can often be triggered by damaged brickwork or leaking pipes within your internal walls, which a professional should deal with.

There are home improvement grants and services available which may help with the cost of getting rid of damp and mould. Find local home energy grants on the Simple Energy Advice website. For severe mould infestation, contact the environmental health department of your local authority for advice and assistance.

Final thoughts

The fact of the matter is that we are all exposed to moulds to varying extents in our everyday activities. Moulds are prevalent throughout our environment. Exposure to damp and mouldy environments can increase your chances of respiratory problems and infections. Ensuring that your home is in the best condition that it can be is the best solution for stopping mould in its tracks.

Some useful contacts for anyone concerned about mould allergies and preventative measures they can take include:

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About the author

Evie Lee

Evie Lee

Evie has worked at CPD Online College since August 2021. She is currently doing an apprenticeship in Level 3 Business Administration. Evie's main roles are to upload blog articles and courses to the website. Outside of work, Evie loves horse riding and spending time with her family.

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