Malassezia fungi feed on certain substances found in skin care products. Fatty acids, oils between the C11-20 carbon chain, some esters, some drying alcohols, some PEG codes, some polysorbates, etc. can serve as a food source for these fungi even in very small amounts. When the fungus reaches a population that is much higher than it should be, it activates killer cells. This metabolic activity results in inflammation of the area. This can lead to thinning of the skin, long-lasting redness patches, itching accompanied by persistent acne, and can contribute to acne formation.