The presence of Malassezia does not guarantee dandruff, as this fungus is commonly present on healthy skin, but it evidently central to dandruff production if other key factors support it.

Fungi provide an alarming array of pathogens, some such as the ascomycete Candida albicans can be serious in immuno-compromised patients such as those with HIV.  They are responsible for a wide variety of diseases in plants and animals.  A somewhat more benign example concerns fungi that result in excess production of flakes from the epidermal skin layer, especially on the head, where we refer to the condition as dandruff.

Several groups of fungi have learnt independently to colonize human skin, and dandruff can be caused by a scalp-inhabiting basidiomycete known as Malassezia globosa. This fungus breaks down natural oliy secretions (sebum) from the skin, releasing oleic acid which then irritates the surface of the scalp causing inflammation and flaking of the affected epidermal cell layer (the ‘stratum corneum’). The presence of Malassezia does not guarantee dandruff, as this fungus is commonly present on healthy skin, but it evidently central to dandruff production if other key factors support it (e.g. sebum levels, allergens, climate and certain irritant food groups).

Malasseiza is a basidiomycete yeast closely related to a variety of plant pathogenic bacteria, but in its transfer to our skin it shows convergence with Candida albicans (an ascomycete yeast). At the molecular level, Malassezia and Candida both share a significant number of genes to deal with skin chemistry (e.g. lipases, aspartyl proteases, acid sphingomyelinases) so that both can meet the common challenge of colonizing on skin and being virulent.