The Peanut Butter Smell Test

There’s been a lot of talk about anosmia or loss of smell as a side effect of COVID.  But anosmia in older persons, occurring without other known causes such as polyps in the nose or chronic sinusitis, may be a sign of developing Alzheimer’s dementia (AD). 

A study conducted in 2013 found that patients with early signs of AD exhibited a significant loss of sense of smell, specifically on the left side of their nose. This simple test, looking for a left/right discrepancy in identifying peanut butter odor, was touted to be a simple, no-cost detector for AD.  After reading this, I admit I high-tailed it into the kitchen to sniff a bit of PB no J.  Ah, thank heavens, peanut butter fumes equally yummy on both sides.

Years later, a group of researchers from the U.S. and Columbia decided to retest volunteers with AD.  While partial or complete loss of smell continues to be a possible symptom of developing AD, the scientists found no disparity in bilateral odor detection in one group of 20 exposed to 20 different aromas.  This group had the opposite nasal opening taped as opposed to the other group of 15 in which one side was squashed by the person’s finger while testing the contralateral side.  The researchers concluded that pushing on one nostril variably distorted smell detection on the other side.  Bottom line:  there is no evidence of a left vs right-sided smell disparity.