They smell completely different to me but complement eachother well.
Peppermint is like a straight mint scent. Its very sharp. To me, it smells like a lot of strong mint gums taste. Main constituent chemically is menthol.
Eucalyptus is also a sharp scent but is very herbaceous and medicinal smelling. Its hard to describe becasue to me there are very few smells that replicate eucalyptus eo in nature. Main constituent chemically is Eucalyptol.
ETA: Posted at same time as luebella! To add: if you want to get a good idea of eucalyptus EO, vicks vapo rub has a lot of it in it.
Its actually got camphor, eucalyptus oil and menthol in it. You can really smell the camphor and eucalyptus in it. Menthol just adds a mintyness to me. Then again most of the time I smell it when I'm all stuffed up so.... :silent: You can also probably find eucalyptus EO in health and wellness stores if they are around you. That way you know how it smells before buying it. Its a very distinct smell. I absolutely love it.
I think your nose would be the best in telling you the difference. I can honestly say that while Vicks smells like it have eucalyptus in it, eucalyptus doesn't smell like Vicks. If you can, before you shell money out for it,maybe you should find a store that sells EOs and smell a few to get an idea of what you'd want to work with.
I had an "order" from my son and my hubby and they both chose blend of mint and Eucalyptus for their after shave lotion. My garden/mechanic soap with Mint and Eucalyptus soap is popular and everyone likes it I use Eucalyptus when I make cleaners for bathroom. It smells so fresh. I kind of smell subtle in my salves
Sorry, no I can't explain it. I do know that when I have a cheap or weak peppermint that needs from bolstering for a peppermint soap (I have about 10 pounds of it in the house right now) I use a bit of eucalyptus or rosemary with it. A few days after its cut the scents all meld together into just a peppermint smell.