Linolenic 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 polyunsaturated fatty acid used for skin conditioning, and laboratory evidence shows that a recent laboratory study found delayed hyphal changes in a tested Malassezia furfur strain under specific conditions. That is a meaningful theoretical concern, but it does not prove that every product containing Linolenic Acid will worsen seborrheic dermatitis.

Concentrated, occluded unsaturated fatty acids also affected irritation and water loss in human skin testing, although that was not a seb derm study. 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 Linolenic Acid; otherwise stop if a product repeatedly increases itching, redness, tightness or stinging.