A subgenus of olfactory receptors (ORs) that are activated by isovaleric acid (IVA) are identified as well as assays that utilize one or more of these ORs. These assays are useful for identifying potential anti-odorants which may be used in deodorants, air and carpet fresheners, fabric deodorizers, and other compositions for camouflaging odor attributable to IVA and related carboxylic acids.