Huffing koala Bear

I bought a vial of concentrated Eucalyptus oil to sniff when I have a cold to clear my stuffy head but my friends with colds laugh and say I'm damaging my brain cells. I say they are missing out because when a pleasant smell comes around during cold season I'll be the only one able to retrieve it. Besides, Koalas use this stuff all the time and if it was dangerous wouldn't they'd all be extinct?