There is research being done on herbal remedies to replace antibiotics in particular.Some other reliable brands of essential oils are Young Living and Mountain Rose Herbs.
I have always felt that one reason we don't see more validating studies of the effectiveness of herbs is that there is no money in it for the big corporations.
Oregano oil is used as an anti-inflammatory and an antibiotic, especially good on respiratory issues.
Even the big corporations and the egg industry have come to realise that tipping antibiotics down everything that has the slightest sniffle, or off day is no longer viable.
I can't see antibiotics as being a bad thing; it's just they have been misused.
I have in the past and would still use them but on the advice of a vet only.
https://thepoultrysite.com/articles/herbs-and-spices-a-sustainable-alternative-to-antibiotics