The answer is yes, you do. Virtually all of us are colonized by this fungal species. But only occasionally does it cause a problem—but when it does, it may be signaling something going on in the body, another example of a body sign of disease like skin tags associated with insulin resistance or xanthelasma associated with an excess of small LDL particles.
You can find Malassezia in many parts of the body including the skin, gastrointestinal tract, human breast milk, even the central nervous system. Malassezia species typically live in these locales quietly and don’t cause any trouble, as is true for several other fungal species. When Malassezia is permitted to overpopulate in the skin, however, it causes a discolored skin rash called pityriasis versicolor (also called tinea versicolor; shown above). While fungi such as Candida albicans and Candida glabrata have been blamed for a variety of fungal infections, such as skin rashes and infections of knee or heart valve prostheses, the only human health condition that has been blamed on the fungal species of Malassezia is the skin rash of pityriasis versicolor. Malassezia species can also be among the microbes complicating other skin rashes including seborrheic dermatitis, atopic dermatitis, and psoriasis. In pityriasis versicolor, the skin discolorations are typically lighter colored spots on dark skin, dark colored spots on light skin, usually over the trunk, upper arms, and neck. Go to any beach during summer and you will see many people with this characteristic skin rash.
Bacteria are the dominant variety of microorganisms in the human body, with fungal species like Malassezia comprising less than 1% of total microbial numbers. But something happens to disturb the quiet coexistence of bacteria and fungi (as well as other microbes, such as Archaea). The disruption might be due to antibiotics that reduce bacterial numbers and thereby allow fungi to proliferate. It could be due to glyphosate, the primary herbicide in Roundup, that acts as an antibiotic against probiotic species like Lactobacillus but ineffective against Gram-negative pathogenic microbes that comprise SIBO. It might be excessive topical use of soap that disturbs the balance of skin microbiome.
Given the increased potential for pityriasis to develop in settings such as kidney failure, steroid use (e.g., prednisone), antibiotic use, reduced immune response, diabetes, autoimmune diseases like lupus, you’ve got to wonder whether this skin manifestation of fungal proliferation is yet another reflection of microbiome disruption in the skin but originating in the gastrointestinal tract. Overgrowth of Candidal species in the gastrointestinal tract is often accompanied by Candidal skin infections and, while it has not yet been formally scrutinized, I speculate that the gastrointestinal tract serves as a repository for fungal species that, in turn, colonize other areas of the body that may include the brain. Could the same situation develop with Malassezia?
Indeed, preliminary evidence is pointing in that direction. H. pylori stomach infection, for instance, may be associated with pityriasis. There is not yet any firm evidence that points towards disruption of the intestinal microbiome that could allow Malassezia overgrowth, but my prediction is that, as with so many other conditions involving bacterial or fungal proliferation, pityriasis will likewise prove to have its root cause in the gastrointestinal tract. Stay tuned as this conversation evolves.