Stearic Acid is best treated as a cautious avoid during an active seb derm flare or when you are following a strict Malassezia-conscious routine. It is a C18 saturated fatty acid used for texture, cleansing and emulsifying, and laboratory evidence shows that some Malassezia species can take up long-chain fatty acids, with species-dependent growth reported when stearic acid was supplied. That is a meaningful theoretical concern, but it does not prove that every product containing Stearic Acid will worsen seborrheic dermatitis.

Growth was not equally strong in every species or test condition, so this is a screening signal rather than a prediction about a cream or cleanser. A small amount in a rinse-off product is also a different exposure from a fatty-acid-rich leave-on cream. If you want the simplest option during a flare, choose a formula without Stearic Acid; otherwise stop if a product repeatedly increases itching, redness, tightness or stinging.