scrubbing mold mould
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Exposure to mould in the home can be damaging to your health, causing allergic reactions and respiratory illnesses.

An inquest found on Tuesday that a two-year-old boy died as a result of a severe respiratory condition caused by prolonged exposure to mould in his home.

But what exactly is mould, when is it harmful, and what can be done about it in your house?

How dangerous is mould?

Mould is a microscopic fungus that grows in damp places. Mould spores are found everywhere and are released in their thousands into the atmosphere.

If you have mould at home you'd notice fuzzy black, white or green patches on the walls and your house might smell damp and musty.

Mould can cause a variety of medical issues, particularly for people who are allergic to the spores. Sneezing, a runny nose and skin rashes can occur, and moulds can also affect the immune system or trigger asthma attacks.

Mould and damp in houses are worse when the temperatures drop in the winter.

Can mould affect your health?

Put simply - yes. People living with damp and mould in their homes are more likely to suffer from respiratory illnesses, infections, allergies or asthma.

Mould can emit spores, cells, fragments and "volatile organic compounds" into the air.

Inhaling or touching mould spores can cause an allergic reaction, such as sneezing, a runny nose, red eyes and skin rash.

Moulds can also trigger asthma attacks and cause coughing, wheezing and breathlessness.

"We know that for people who already have asthma, mould can be a trigger for them," said Dr Andy Whittamore, a GP and clinical lead at the charity Asthma and Lung UK.

"For people who do not have asthma, they can develop an allergic response to mould. In some cases, mould can be breathed in and can be found growing in the lungs - it can be life-threatening for some people."

Those more at risk include the elderly, children and babies, people with respiratory illnesses, people with some skin problems and those with a weakened immune system, either due to illness or because of medicines they are taking.

What causes mould in buildings?

Condensation is the leading cause of mould in homes across the UK.

It most commonly occurs in parts of the home where there are high moisture levels - in bathrooms, kitchens, and around windows.

It happens when the temperature falls to a point, known as the dew point, that water vapour in the air forms into water droplets.

If water vapour comes into contact with a surface in your home that's below the dew point, like an uninsulated external wall or a cold window, then water droplets will form.

If left, it can become damp and create the conditions for mould to grow.

Catherine Noakes, professor of Environment Engineering for Buildings at the University of Leeds, said some homes are more prone to this.

"They are often older buildings, poorly insulated and poorly maintained," she said.

Mould can also be caused by daily tasks which create excess moisture.

"Sometimes it's occupant behaviour - things that we all do and we cannot change," Prof Noakes said.

"We all shower, we all cook, and we all dry washing at home."

Prof Noakes said damp and mould conditions could be made worse this winter if people don't put on the heating because of high energy bills.

How to prevent mould

Prof Noakes says that in severe cases, there are limits to what occupants can do.

In less serious cases there are a number of ways to combat mould, from taking shorter showers to making sure there is more ventilation in your property.

"The shorter the shower, the less moisture there is," Prof Noakes said.

She also suggests wiping down the shower afterwards, rather than leaving the water to evaporate.

The kitchen is another area where moisture rises, so open the windows or use the extractor fan when cooking.

Prof Noakes adds it was also important to check for obvious problems, including leaky pipes or gutters which could be contributing to the problem.

What rights do tenants have?

Sometimes the problems are too severe for occupants to deal with themselves.

Private and social landlords have a responsibility to make sure homes are fit for habitation.

If you are living in a rented property, it is the landlord's responsibility to fix a mould problem if it is caused by disrepair, according to Shelter.

"Where the mould is caused by disrepair or the property is unfit for habitation - for example, as a result of damp or condensation caused by poor insulation or faulty heating or ventilation systems - then it is the landlord's responsibility to fix it," said John Gallagher, principal solicitor for the charity.

If the mould is so bad that it makes your home unfit for habitation, then you could be classed as homeless and entitled to emergency accommodation, he added.

But Mr Gallagher said if there is evidence a tenant is not ventilating the home correctly, then the landlord may not be responsible.