Moulds are microscopic fungi made up of clusters of fibres. They live on plant or animal matter, which they decompose (break down) for their nourishment. There are thousands of types of mould (spelled mold in the USA), and they all need moisture to grow. Mould can grow indoors (for example in damp bathrooms and kitchens) and outdoors (for example in compost or in a garden shed).

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Allergy to Mould

For some people, the spores that moulds release into the air can cause allergic reactions. If you think you or your child may have an allergy to mould, consult your GP.

Not all symptoms triggered by dampness and mould are allergy related. There is strong evidence from studies that, for some people, symptoms triggered by dampness and mould can have non-allergic causes. Your doctor would need to consider this possibility and, in our view, should refer you to a specialist.

The rest of this article focuses on actual allergy to mould.

Symptoms of mould allergy

Symptoms of mould allergy vary from person-to-person but typically include sneezing, wheezing, itchy or watery eyes, and runny nose. Mould allergy can cause a condition identical to hay fever in the late summer and autumn. Mould can also aggravate asthma.

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.

Treating allergic reactions triggered by mould

Your doctor may prescribe an antihistamine to treat mild symptoms. A nasal spray, eye drops, or both may also be considered when the symptoms are similar to hay fever.

If you have asthma and are allergic to mould, it is important that your asthma is well-managed:

• Short-acting reliever inhalers (usually blue in colour) treat asthma symptoms by relaxing the airways quickly to allow you to breathe more easily.

• Preventer inhalers (usually brown in colour) help prevent asthma symptoms by reducing swelling and inflammation in the airways. They are normally prescribed for people who would otherwise need to use a reliever inhaler three or more times a week.

Taking your preventer inhaler as prescribed means you are less likely to have asthma symptoms and reduces the risk of having a severe asthma attack. Your GP or asthma nurse will be able to advise which type of asthma treatment is best for you.

Avoiding exposure to mould

There are steps you can take to reduce exposure to mould if you have a mould allergy.


• 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 wish to buy a dehumidifier, which will collect moisture from the air. You can also prevent the spread of damp air throughout the house by keeping doors closed when you are showering and cooking. If your double glazing does not have trickle vents, consider having these fitted.

• Avoid drying clothes indoors. As wet clothes dry, they release moisture into the surrounding air, which helps provide the damp conditions mould needs to grow. If possible, dry clothes outside or in a tumble drier. Vented tumble driers must be vented to the outside. If you have a condenser or heat pump drier, ideally this should be plumbed in, or alternatively, ensure it is emptied regularly. If you must dry clothes on an airer indoors, ensure there is good ventilation by opening windows.

• Use a mould killer. If you have visible mould indoors, clean it down with a cloth. You can also use a mould killer, easily available on the high street and in supermarkets.

• Check damp walls. Look for mildew, especially behind wallpaper. Treat with mould killer and a coat of sealer and/or paint.

• Beware of areas prone to high humidity. These include basements and shower cubicles.

• Be aware of other possible sources of mould. These include indoor plants (especially the material in the container that they grow in). Also, items that have been subject to high humidity or an accidental soaking, such as mattresses, pillows, carpets and foam furniture (especially if they have a musty smell).

• Check if the house has evidence of damp. Ensure that guttering is working correctly to stop water running down the outside wall and look for evidence of rising damp in walls. If in doubt, request a damp survey.


• Wear a dust mask. If you are digging in the soil, cutting grass, or collecting decaying leaves, wearing a mask can help prevent you from breathing in mould spores. The Health and Safety Executive provides information on dust masks.• Avoid damp woodland. Mould is common where soil is moist and leaves are rotting.

• Be extra aware at certain times. Outdoor moulds multiply in the late summer and autumn, for example on warm humid days in the late afternoon and evening.

Might I react to food?

People with allergy to mould spores often ask if they might have an allergic reaction when they eat food contaminated with mould, or foods such as mushrooms, yeast or Quorn (mycoprotein derived from fungus). While isolated cases have been reported, having discussed this with medical experts we believe this happens only very rarely. However, we are not aware of any studies that have been done to determine whether this is a significant risk.

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