May have the capacity to recognize and bind specific classes of odorants. May act as a carrier molecule, transporting odorants across the mucus layer to access receptor sites. May serve as a primary defense mechanism by recognizing and removing potentially harmful odorants or pathogenic microorganisms from the mucosa or clearing excess odorant from mucus to enable new odorant stimuli to be received (By similarity). Highly expressed in olfactory mucosa but undetectable in thymus, kidney, lung, brain, spleen and liver. Belongs to the BPI/LBP/Plunc superfamily. BPI/LBP family.