AcylCoA:cholesterol acyltransferase (ACAT) is an intracellular cholesteryl ester synthase tied closely to the absorption of dietary cholesterol. Oleyl analide (OA) is a weak inhibitor of acylCoA:cholesterol acyltransferase (ACAT) with an IC50 of 26 μM. OA and the related glyceride dioleoyl phenylamino propane 1,2-diol have been linked to a syndrome of eosinophilia, excessive T-cell activation, and elevated interleukin-4 (IL-4), soluble IL-2R, and IL-5. The clinical consequences are an acute pulmonary inflammatory reaction followed by chronic neuropathy, myalgia, and autoimmune connective tissue disease, generally referred to as toxic oil syndrome (TOS). Aniline-denatured cooking oil is a source of OA associated with TOS.