yep it smells a bit like euchalyptis oil

Its actually melaluca. You can actually order medicinal quality 100% melaluca extract from most health food stores. I had toyed with the idea of making my own melafix at 30-60% potency for a time, but never got around to procuring the emulsifying agents I needed to get the melaluca oil to disperse in water. But based on my pricing you could make 10 gallons of melafix for the same price as a bottle using the ingredients to make your own.
I have heard that a small amount of normal dish detergent can be used and is safe but I never tried it for obvious reasons.