Dr Peter Cook is a Wellcome Trust Sir Henry Dale Fellow at the MRC Centre for Medical Mycology. Peter’s research focuses on understanding how the lung-airway environment influences innate immunity to mediate anti-fungal allergic disease.
In our interview with Dr Cook, we explore his work on the relationship between mould and human health, the scope of the UK’s mould problem, and whether a “safe” level of mould exposure exists.
What is your area of expertise in mould research?
My training isn’t in fungi but rather as an immunologist. I did my PhD in parasites, focusing on how our immune response reacts to these large parasites that infect people around the world.
What does your day-to-day role look like?
We try to understand why we get diseases like asthma and how we can treat them more effectively.
"Most treatments for chronic diseases aren’t curative - they don’t actually get rid of the disease, they just manage the symptoms."
And I’ve always thought, wouldn’t it be better if we could actually treat the root cause and cure the disease?
What should the public know about mould and the risks associated with its exposure?
Firstly, mould is everywhere, so don’t panic if you have some exposure to mould in your environment - it’s part of the natural world. Put simply, mould is a fungus that releases a huge number of microscopic spores.
"The real concern revolves around how many of those spores we end up breathing indoors. We as humans live in these warm homes which are perfect environments for harbouring mould so trying to minimise the level of humidity in our homes is essential."
Simple steps to help this can be opening windows to create airflow, fixing damp areas promptly, avoiding drying clothes on radiators, regular cleaning and spending more time outside. We still don’t know the exact spore-count that tips someone into higher risk, but until better data emerges, the safest strategy is to minimise indoor spores while remembering that a bit of mould is normal.
If mould is everywhere but a lot of it's invisible, how do we know when we’re living within safe parameters?
The truth is, within the mould research space, we still don’t have a clear definition of what ‘safe’ levels actually are. So for now, it comes down to common sense. If you see visible mould in your home, remove it properly. If you're gardening or handling compost - activities that release a lot of spores - it’s a good idea to wear a mask. But again, mould is present in every environment, so there’s no need to panic. It's more about doing what you can to reduce unnecessary exposure. When it comes to chronic conditions like asthma, it may take a long time for you to develop these conditions so even a small change to reduce exposure could have a massive reduction of risk. But that’s exactly why more research is needed, so we can better understand the risks and eventually offer clearer, evidence-based guidelines.
How extensive do you think the epidemic in the UK really is?
The short answer is we don’t know. There’s a real lack of empirical data as very few studies have properly investigated the extent of mould in people’s homes across the UK. And those are exactly the kinds of questions we need to be answering.
"What we do know is that the UK has a lot of older, poorly ventilated housing, and we live in a relatively wet and mild climate which are conditions that are ideal for mould growth."
There have been some great studies looking at things like indoor pollution or mapping traffic-related air quality across cities like London, but when it comes to fungal exposure, we just don’t have that same evidence base yet. That’s why ongoing research in this area is so important.
What would you say needs to change in terms of public health policy or just general education around mould?
I think there are a few key avenues we could go down. The first is to try and make people aware of what mould is, the potential risks and how you can fix it. So providing people with the information to fix it rather than scare people.
"From an educational standpoint, we also need to talk more about fungi in general as it’s often overlooked as a driver of many diseases. There's a lot of emphasis understandably on bacteria and viruses, but I think getting people to understand the consequences of some of the diseases fungi can contribute is equally important."
In terms of policy, improving housing standards across the UK would make a huge difference. I know there are efforts underway in that space, and I think continuing to push for better, healthier living conditions should be a major priority as a good housing policy is good health policy. And finally, we have to consider mould exposure in the broader context of overall health. Fungal spores are certainly a risk factor, but they often interact with others like poor diet, lack of exercise, or pre-existing respiratory conditions. So promoting healthier lifestyles more broadly is also part of the solution.
What have you uncovered so far in your research around the interplay of mould and our health?
Our team is focused on researching how the immune system responds to mould exposure. Specifically, we've identified which immune cells are critical in driving the response. The immune system is made up of many different cell types, and through our research, we now have a clearer picture of which ones are most involved when the body reacts to fungal spores. We’ve reached these conclusions using both animal models and samples from patients with asthma who are highly sensitised to fungi. By studying samples from their airways, we’ve been able to explore how their immune systems respond to mould at a cellular level.
Another key part of our work has focused on the spores themselves and understanding what it is about them that triggers the immune system. We now have a better idea of the exact stage in the spore’s growth that begins to activate this response.
"Spores grow very quickly, within about 12 hours they start forming these filament-like structures called hyphae. We've managed to narrow down the critical time window when the immune system first recognises and reacts to them."
The next step in our research is to understand what the spores are expressing at that key stage and what signals or molecules are triggering the immune reaction. Now that we know which immune cells are involved and when the response happens, we’re trying to pinpoint exactly what they’re reacting to. It’s very difficult to accurately diagnose someone who is sensitised to fungi, and treatment options are limited. But if we can fully understand this process, we can develop better diagnostic tools and potentially, more effective treatments that target the root cause of the immune response, rather than just managing the symptoms.
What do you do for yourself, your family, and your home to avoid the health implications of mould?
We’re fortunate to lead a fairly healthy lifestyle. We stay active and spend a lot of time outdoors. At home, we try to keep things clean and well-ventilated. We have a golden retriever who sheds a lot of hair, so staying on top of tidying is essential anyway! With two children, we’re also mindful of our air quality. We make a point of opening windows regularly to improve airflow and reduce humidity. One specific thing we try to avoid is drying clothes indoors, especially on radiators, as that creates a warm, damp environment which mould loves. So whenever possible, we dry clothes outside. It’s really about taking simple, practical steps to reduce moisture and improve ventilation. Those small habits can make a big difference.
