Polysorbate 60 is worth treating with caution during an active seb derm flare or in a strict Malassezia-conscious routine. It is a stearic-acid-derived emulsifier, and laboratory studies found that Malassezia could grow when polysorbates 20, 40, 60 and 80 were supplied as lipid sources. This is a laboratory screening concern, not proof that Polysorbate 60 causes flares in people.

The result depended on the species, culture conditions and how the lipid was presented. A small amount used to keep a rinse-off cleanser mixed is not the same exposure as a leave-on formula. During a flare, a formula without Polysorbate 60 is the simpler cautious option; otherwise stop if repeated use brings more itching, redness, tightness or stinging.