15(S)-HETE is produced from arachidonic acid by the enzyme 15-LO. In humans it is formed primarily in the respiratory epithelium, leukocytes, and reticulocytes. It may contribute to allergic rhinitis, has anti-inflammatory properties, and acts as a vasoconstrictor. Cayman's 15(S)-HETE ELISA is a competitive assay that permits the measurement of 15(S)-HETE within the range of 39-5,000 pg/ml, typically with a sensitivity (80% B/B0) of 170 pg/ml. This assay is very specific for 15(S)-HETE, showing very low crossreactivity to other HETEs.