There is an at-home method for doing this called olfactory training. You'll need four oils, which you can find at health food stores: Phenyl ethyl alcohol (rose) Eucalyptol (eucalyptus) Citronellal (lemon) Resinous (cloves) Twice a day, spend five minutes exposing your nose to each smell. Sniff one for 10 seconds, wait 10 seconds, and sniff the next.