Hanging the washing out to dry in the garden has been a rare sight these last few months, with winter storms bringing freezing temperatures and 100 mph gusts of wind. But does the way we dry our clothes indoors actually matter?

Drying wet clothing on racks in poorly ventilated spaces could increase the amount of mould growing in your home, which is associated with poor health and, in some cases, even death.

When mould grows in your home, it can form black or green coloured patches on the walls, and usually creates an unpleasant musty smell. It shouldn't be ignored, because being exposed to mould over long periods of time can have serious health implications.

Mould is a broad term for a group of fungi that produce tiny particles called spores. Fungi produce spores when conditions are right for their growth, which can include cooler temperatures and high humidity.

This is why you're more likely to find mould growing on bathroom ceilings or damp walls, where there is more water for fungal spores to settle and grow.

There are many different species of mould. The most common ones to cause problems in damp homes are penicillium and aspergillus. It's estimated that we breathe in small numbers of spores from these fungi on a daily basis.

Luckily, our immune system is very good at spotting and killing fungal spores, which limits the number of fungal lung infections in humans even though we're constantly exposed. Immune cells called macrophages sit inside the air spaces of the lungs (called alveoli), and these cells eat anything you inhale that could be considered harmful, including fungal spores.

Risks for compromised immune systems

However, there are many people whose immune systems are not able to remove fungal spores, and in these cases the fungi can cause dangerous infections or make underlying health conditions (such as asthma) much worse.

People who have damaged or compromised immune systems are at higher risk of becoming seriously unwell from fungal infections. Moulds like aspergillus cause infections in patients with limited immune function, or who have lung damage from diseases like asthma, cystic fibrosis and chronic obstructive pulmonary disease (COPD) associated with heavy smoking.

In people with asthma, the immune system overreacts to triggers (including fungal spores) causing inflammation in the lung. This inflammation makes it more difficult to breathe by reducing the size of the airways.

The same type of immune response is responsible for the symptoms of asthma and allergic responses, and fungal spores can also trigger these same types of immune responses. This means that fungal spores can be a particularly powerful trigger for some people.

In very extreme cases, the fungal spores don't just cause inflammation but can invade the airways and block them leading to bleeding within the lung. This happens when spores germinate and form long spiderweb-like projections called mycelium which create sticky lumps that block airways and damage the delicate tissues of the lung. Growing resistance

Aspergillus infections are treated with antifungal drugs called azoles, which prevent the fungal cells from forming properly. Azoles are very effective, but there are increasing rates of resistance to azoles reported in aspergillus which is a significant cause for concern.

We have a limited range of antifungal drugs available to treat mould infections – and when resistance develops this can severely reduce the options a patient has for treatment.

Resistance to drugs such as azoles can develop in patients who take these drugs for long periods of time, but recent research has indicated that resistance is more commonly developing in the environment, where most fungi are found. This means that even before a patient is diagnosed with an aspergillus infection, it may already be too late for the antifungal drugs to be effective.

Development of drug resistance in environmental fungi has been linked to use of azoles and other antifungal drugs in farming. Fungal infections are a big problem for cops, and plants need protection from these infections the same way we do. Unfortunately, the same drugs we use in the clinic are the same types that are being used in agriculture.

Climate change may also be driving drug resistance in environmental fungi. Exposure to high temperatures was recently found to help moulds develop resistance to commonly prescribed antifungal drugs.

There have also been reports of patients becoming ill from species of mould that were not thought to cause human disease, in part because they could not grow at the human body temperature.

More mould species could therefore be picking up the ability to cause infections, as well as becoming drug resistant. Research programs and healthcare initiatives that monitor for these changes are vital to help us become prepared for potential increases in mould infections.

While a healthy immune system means that typical exposure to fungal spores is not likely to cause you any health problems, being exposed to very large amounts of fungal spores can prove to be fatal even for people who don't have underlying health issues.

In 2020, toddler Awab Ishak died as a direct result of high exposure to fungal spores, caused by excessive damp and mould in his home.

His death led to a change in UK law (Awaab’s Law) which requires landlords to respond promptly to damp in homes they manage, to ensure that tenants are not exposed to excessive levels of fungal spores which can effect their physical and mental health.

It's important, then, to help keep your home free of mould. The best way to do this is ensure you have good ventilation and take other measures to reduce damp, such as using a dehumidifier or investing in a heated clothes rack to dry your clothes indoors in the winter.