Oregano and thyme both contain the chemical componant called "thymol". Thymol is the chemical that is antiseptic, anti-virul and anti-fungal. It is also anti-microbial. Thyme has higher thymol levels per milligram than oregano - that is why it is the main ingredient in Listerine Antiseptic Mouthwash.
I said all that to say this - HUMAWORM contains thyme instead of oregano because of the higher thymol levels per milligram - it does not take as much to do the same thing as oregano. SO, supplementing with oregano oil should be O.K. - just use a moderate amount. Thanks!