Is black mould dangerous, and who is most at risk?

Black mould in a home deserves attention, especially where it keeps returning or covers a large area. Government guidance treats damp and mould as a health concern for anyone, with some people more vulnerable than others. You do not need to identify a mould species before dealing with the dampness and arranging for the growth to be removed. Start by finding where the moisture is coming from; cleaning the surface alone will not settle a recurring problem.

What are the health concerns?

Damp and mould primarily affect the airways and lungs, though eyes and skin can also be affected. Government guidance lists cough, wheeze and shortness of breath among possible respiratory effects. It also says dampness alone can increase the risk of health problems, even without visible mould. This is why a musty, damp room deserves attention as well as an obvious patch on the wall.

The useful response is to take the condition seriously, understand how extensive it is and act on the source of the moisture. A photograph can help record where growth was found before cleaning, especially when it is intermittent or in a rented home. Look at the position of the patch and what might be bringing water to that part of the room.

Who needs particular care?

Anyone can be affected. Government guidance says more urgent attention is particularly important for people with existing conditions such as allergies, asthma or other lung diseases, and for people with weakened immune systems. It also identifies pregnant women, children and young people, and older people among those more vulnerable to significant health impacts. These are reasons to deal with the housing problem promptly, not labels to put on a family member's symptoms.

People who are bedbound, housebound or have mobility problems can have more difficulty getting out of a damp and mouldy home. A person may also fall into more than one of the groups identified in the guidance. If you rent, explain any relevant vulnerability when reporting the problem so the landlord can assess the situation with that information. The guidance says landlords should not wait for medical evidence before acting on damp and mould.

What to do when you find mould

Look at the room and the building, not just the stain. Check whether a gutter or roof is letting water in, whether there is a plumbing leak, or whether moisture is collecting on a cold surface. Condensation often shows on windows and cold external walls. The source may be less obvious than the patch itself, and more than one source can be involved. If you cannot establish the cause, ask an independent building surveyor with suitable damp and building experience to investigate.

Small amounts of mould on a hard surface can be cleaned with an appropriate mould and mildew product, then left to dry completely. Follow the product instructions, wear protective equipment and ventilate during the clean. Larger areas should be handled by qualified professionals. If mould has reached absorbent materials, cleaning may be difficult or impossible. Do not treat a wipe-down as proof that the problem has gone: the moisture source still needs attention.

If the home is rented, report the mould and any leaks or ventilation faults promptly. Describe where it is, whether it is spreading and whether it returns after cleaning. The landlord should assess its extent and underlying causes, address the source and keep the occupants informed about the steps being taken. If you are concerned about symptoms you are experiencing, government guidance says to consult a healthcare professional. Housing action need not wait for that conversation.

Yorkshire and Lancashire bedrooms: look beyond the visible patch

In a shared bedroom in a terrace or back-to-back, a bed may end up close to a cold back wall. If a patch is growing there, check the wall, the nearby window and any furniture that hides part of the surface. Leave a gap between furniture and an external wall where practical, and keep room vents clear. Moisture from cooking and bathing can move through a home before settling on colder bedroom surfaces, so also check that the kitchen and bathroom extraction works.

A cold wall does not by itself tell you whether the moisture came from indoor air, a leak or rain outside. Take note of where the mark appears and whether it changes after wet weather or when the room is used. In a rented home, share those observations when reporting it. Where the source is uncertain or the growth continues, a suitably experienced independent surveyor can investigate the building and recommend proportionate repairs. The priority is a dry room, not simply a freshly cleaned wall.

This page gives general information, not legal or medical advice. For your own situation, use the organisations listed under "Where this comes from" at the foot of the page.