Good distinction, Bobad. Perhaps I should have said "partially digest" instead of "decompose." However, when you "tenderize" meat by hanging it in the fridge for a few days, you're not introducing enzymes.
Rowan, The particular melaleuca species used by Melaleuca, Inc. is "melaleuca alternifolia." And their products are backed by research findings that the US FDA considered sound enough to authorize the claims that the oil is "antiseptic," "analgesic," "antifungal," and that it penetrates all the layers of the skin, is aromatic, and has a couple other beneficial properties. There are a number of different compounds found in the oil from various melaleuca species, partly depending on the tree itself and partly depending on processing. Some compounds are more healthful/beneficial and others are more caustic, so the standards I referred to above have to do with the proportions of various compounds in the oil. Most of the "tea tree oil" I find on the market has no information about such proportions of various compounds.
FWIW, I'm not at all surprised that a botanical oil, of whatever sort, had 'expired' 20 to 30 years after being bottled. Or at least that "nobody was prepared to guarantee their biological properties. LOL
I, myself, have some applesauce and tomatoes and blackberries that I canned back in the early 1980s. I can't bring myself to throw them out - yet. But I'm also afraid to just open them up and eat them, because I don't know whether and to what extent that might be dangerous.
(Continuing this tangent) I'm not surprised that Melaleuca Oil didn't work on flea bites or that it might have even made the irritation worse. I don't think the oil is touted as an "anti-itch" solution, and since it's a solvent, it probably would carry the itch-causing agent further into the skin. My own experience, however, does strongly back up the claims that it heals burns, works as a better (and less painful) antiseptic for cuts, is an excellent remedy for gingivitis (when swished around the gums or massaged in) and toothache (not drying like oil of clove), and helps treat fungal outbreaks (e.g., athletes foot), dandruff, etc. But I don't find it to be a substitute for cortisone for itching. And, while antibiotics may work on various ailments, I consider them a last resort, if only because the more they are used, the more antibiotic-resistant strains of bacteria seem to develop. (Not to mention that they kill off beneficial bacteria and tend to have side effects like diarrhea.) But I have sometimes treated a cut or abrasion with a combination of Melaleuca oil (for cleansing and pain relief) and antibiotic cream.