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First, do no harm. What part of this dictum don’t they understand?

Don’t let a child play with fire. Or a guitarist with science. A person who doesn’t understand that living beings are complicated will choose molecule A to get effect X, without thinking about side effects Y and Z. That’s OK, unless Y is basal cell carcinoma. And Z is killing melanocytes (think Michael Jackson and vitiligo).

A new skin “care” product has this ingredient list:

INGREDIENTS: Water, Dimethyl Isosorbide, Glycerin, Olive Oil Glycereth-8 Esters, Niacinamide, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Coconut Alkanes, Malassezin, Rhododendron Ferrugineum (Alpine Rose) Extract, Sodium Hyaluronate, Bisabolol, Carnosine, Tocopherol, Tetrasodium Glutamate Diacetate, Silica, Coco-Caprylate/Caprate, Chlorphenesin, Sodium Phytate, Pentylene Glycol, Caprylyl Glycol, Citric Acid, Sodium Hydroxide, Disodium Phosphate, Sodium Chloride, Phenoxyethanol

What is malassezin? It’s a chemical produced by the yeast Malassezia.  Malasezzia is a fungus that seems to be a complicating (if not causal) factor in seborrheic dermatitis, dandruff, folliculitis, psoriasis and onychomycosis.  It also causes pityriasis (tinea) versicolor, an infection that involves the loss of melanin and causes patches of discolored skin. 

A new company obtained a patent to use the fungal chemical malassezin (and derivatives) to treat hyperpigmentation. The way this chemical works is by binding to a receptor that deals with xenobiotic (foreign) /toxic chemicals, the hydrocarbon receptor (AhR), synonym, dioxin receptor. This is not a well-known receptor but it has many biological functions (in addition to mediating the detrimental effects of dioxin intoxication in the skin and other organs.   It’s not surprising that chemicals that bind to this special receptor can produce some nasty effects And guess what? It seems that Malassezia-synthesized aryl hydrocarbons bind to the receptor (AhR) and may lead to basal cell carcinoma through UV radiation-induced carcinogenesis. This includes the chemical included in the ingredient list I posted above.

A bit less dramatic but still worth noting: these chemicals have been linked to M. furfur strains isolated from cases of seborrheic dermatitis, dandruff, and pityriasis versicolor. Upon ligand binding, AhR translocates to the nucleus, where it dimerizes with the aryl hydrocarbon nuclear translocator, binds to xenobiotic responsive elements flanking the 5′ ends of genes, and modifies their transcription in a ligand-, cell type-, and tissue-specific manner. AhR functions in skin physiology by affecting the cell cycle and melanogenesis; it also modifies responses to injuries and affects wound healing, UV damage, and modifies the inflammatory response to immune signals.

This is playing with fire. I hope that the company has good insurance.



Gaitanis G, Magiatis P, Hantschke M, Bassukas ID, Velegraki A. The Malassezia genus in skin and systemic diseases. Clin Microbiol Rev. 2012 Jan;25(1):106-41. doi: 10.1128/CMR.00021-11. PMID: 22232373; PMCID: PMC3255962.

Gaitanis G, Velegraki A, Magiatis P, Pappas P, Bassukas ID. Could Malassezia yeasts be implicated in skin carcinogenesis through the production of aryl-hydrocarbon receptor ligands? Med Hypotheses. 2011 Jul;77(1):47-51. doi: 10.1016/j.mehy.2011.03.020. Epub 2011 Mar 27. PMID: 21444158.

Grimes PE, Bhawan J, Howell MD, Desai S, Coryell E, Nashawati R, Einziger M, Simpson AM, Yaroshinsky A, Mc Craw T. A novel proof-of-concept study assessing the lightening effects and safety of malassezin for treatment of facial hyperpigmentation. J Am Acad Dermatol. 2022 Aug;87(2):456-458. doi: 10.1016/j.jaad.2021.10.008. Epub 2021 Oct 19. PMID: 34678236.

Krämer, H.-J., Podobinska, M., Bartsch, A., Battmann, A., Thoma, W., Bernd, A., … Mayser, P. (2005). Malassezin, a Novel Agonist of the Aryl Hydrocarbon Receptor from the Yeast Malassezia furfur, Induces Apoptosis in Primary Human Melanocytes. ChemBioChem, 6(5), 860–865. doi:10.1002/cbic.200400247 

Vlachos C, Schulte BM, Magiatis P, Adema GJ, Gaitanis G. Malassezia-derived indoles activate the aryl hydrocarbon receptor and inhibit Toll-like receptor-induced maturation in monocyte-derived dendritic cells. Br J Dermatol. 2012 Sep;167(3):496-505. doi: 10.1111/j.1365-2133.2012.11014.x. Epub 2012 Jul 19. PMID: 22533375.