During the conversation, Thomas Dawson remarkably often answers questions with: ‘we just don’t know that yet’.
It seems much remains unknown about the most abundant bug on our skin: it’s a yeast, and it’s called Malassezia.  It is conventionally known as the dandruff fungus, but that’s only when it becomes annoying. Every human being is colonised by Malassezia. It becomes part of our life from the day we are born; within weeks the skin of a newborn baby is covered by it. Where there is oil, the yeast is present as oil is its nutrition. On our heads, our chest, our backs, Malassezia is present everywhere except on our feet, which are the domain of bacteria.
‘Do we need Malassezia or does it need us? What is it doing there?’ These are the questions, says Dr Dawson.


Thomas Dawson of the Skin Research Institute in Singapore and Teun Boekhout of Westerdijk Fungal Biodiversity Institute organised a three-day ‘Workshop on Malassezia’, attended by 65 participants from 24 countries. They all have different backgrounds: some study the clinical importance, others its basic biology, interactions with the immune system, or its planetary biodiversity.
But they have one thing in common:  all are puzzled by this yeast. Most people don’t even notice it, until, all of a sudden, it causes dandruff, skin lesions or it starts to itch. ‘What changed: the person, the environment, or the bug?’ The question is asked by Dawson and yes, we could call him an admirer of the yeast.
So much is still unknown about Malassezia and there are many indications it is even more complicated than we know, and ever so interesting. It has been known for 120 years, yet it can only be well cultivated on complex media for the last 20. That’s one reason the research is still in its infancy.


Teun Boekhout summarises: ‘We know a lot, but we understand little. Malassezia is a big enigma'. Take for example sex: scientists think the yeast has sex, probably on your head right now, because the yeast contains all the right molecular machinery. All evidence points in the direction of sex, yet so far nobody caught them in the act. Well, this year one of the participants came up with something that looks like proof, still it is not yet definitive.
Malassezia is not only found on vertebrates- it also exists on corals, sponges and nematodes. And it is biologically active in those environments: but what is it doing? 
The bug seems to influence our immune system, sometimes it may even regulate it (regulate us?). At least, says Dawson: ‘Sometimes we see Malassezia secrete multiple molecules that are known to regulate the immune system. It looks like it sometimes sends out a signal: calm down, everything is cool! Sometimes it says: things are not right here, you need to inflame’.


Although he often answers questions with ‘We don’t know' he does know something: Maybe Malassezia is useful for us, but definitely ‘the bugs are in it for themselves’.
Paradoxically, for a bug that sometimes causes disease, there may be a benefit for both sides, for the carrier (humans, cats, dogs) and for the bug. That may explain the abundance of the fungus.
Most researchers study microorganisms because they make us sick but Dawson is mainly interested in their role on healthy human beings. The yeast also inhabits the skin of healthy people and Dawson wants to know what makes the equilibrium. Which biomolecules come from the bug that tell the skin to be healthy? Can we find out which chemicals those are and can we use them to set things straight? Skin issues can be very diverse, very unpleasant and sometimes for life. That is why Thomas Dawson is dedicated to his research. And with him, Teun Boekhout and the other participants of the Malassezia workshop. The outcome of the workshop is promising. The participants formed mixed groups with scientists from different backgrounds to work together on different topics.
They will meet again, and we’ll keep you posted.

Malassezia globosa in Pityriasis versicolor-SEM  :  Prof. Yuping Ran.