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Is mould dangerous? Black mould dangers & advice

How dangerous is mould? Find out below and learn how to treat it.


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Key steps:

If you find a large (10 sq. ft) patch of mould, or you feel the mould is dangerous to your health, you should:

  1. Try to ventilate the area immediately.

  2. Call a professional to come and look at the mould.

  3. Arrange to stay somewhere out of the house for a few days.

There are an estimated 1.5 million species of mould in the world, with only 100,000 of them having been identified. But is mould dangerous to your health? Most mould is harmless, and the majority of people who come into contact with household mould will be unaffected, but some people can react to it. Learn more about the different types of mould, the symptoms people can get from living in mould-affected areas, and some ways to stop it from spreading in your home.

The term ‘toxic mould’ is a bit misleading – it’s mould that can produce toxins, but the mould itself isn’t toxic or poisonous.

How does mould grow? And are spores dangerous?

Before we cover the different types of mould, it’s important to know where it comes from.

Mould grows in damp places and reproduces by releasing spores which can spread through the air, water, or on animals. It’s while these spores are travelling that humans are most likely to breathe them in.

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How dangerous is mould?

There are 3 categories of mould which can help us understand the risk it poses to us:

  1. Allergenic. This is a mild form of mould but it can cause problems for people with allergies or asthma. Mould spores entering the nose can cause allergy-like symptoms such as sneezing, runny noses, and itching.

  2. Pathogenic. This mould is potentially dangerous if you have a suppressed immune system. Pathogenic mould can cause infections similar to pneumonia in infants, the elderly, and people who are undergoing chemotherapy.

  3. Toxigenic (or ‘Toxic Mould’). Inhaling these spores will make anyone sick and it’s commonly associated with black mould. If you suspect you have black mould in your home, call a professional to investigate and treat it.

How dangerous is black mould?

Black mould (or Stachybotrys chartarum) is not as common as the allergenic or pathogenic moulds but it can be dangerous. Different types of mould can produce different symptoms: severe examples of black mould dangers include causing the lungs of humans and animals to bleed.

Is black mould dangerous and hard to detect?

Black mould is hard to see as it usually grows behind walls and under ceilings. It’s also resistant to the typical air-sampling method used to detect mould and as a lot of moulds can look dark in appearance it can often be mistaken for more harmless varieties.

If you’re in any doubt, call an expert and seek their advice.

How to reduce mould in your home

Is mould harmful? Sometimes. Is mould unattractive? Always. For this reason, learning to remove it and prevent it growing back is essential. The techniques for keeping your home mould-free are fairly easy to follow. Not only will you experience less mould; you’ll have an airier, comfier home as well!

Here’s what you can do:

  • Keep your home ventilated. Turn on extractor fans in the bathroom or kitchen when bathing or cooking. Or just keep your windows open more regularly.

  • Keep an eye on the moisture in your home. Make sure your home doesn’t have any plumbing problems and get rid of anything water-damaged that can’t be dried fully.

  • Keep the humidity low. Indoor plants, fish tanks, and humidifiers all increase humidity in a home.

Remember, mould can grow almost anywhere but the majority of it isn’t harmful to a lot of people. Check out more of our advice on mould, and how to remove it if you find a small patch.

Originally published