I just thought I would link here to a thread started by 10meters last year which is also about oil of oregano. Interestingly this poster also suggested buying from Puritan's Pride:
oregano oil#######Anti-pleomoantibacterial, antifungal, antiparasitic, antiviral
In my own case I use oil of oregano from:
New Product - One ounce of Oil of Oregano in Glass Eyedropper Bottle
I can attest to the fact that this oil is very strong. It has been awhile since I used this and probably should try it again. It was so strong that it would bring short strings of whatever this is to just under the surface of the skin in my fingers and arms. I think this must have been in the blood or lymph as sometimes I could press down, bring it to the surface and wipe whatever this is off. Usually it was colored blue, like ink which made me suspect that in my case that the fish passed on one of those tiny parasites from the sea which do have this capability. Sounds a bit far out though, so I don't push that view and certainly have never said anything like that to my doctor.
As BO mentions this oil has to be added to capsules to take internally. My herbalist had me work up gradually to a few half capsules a day.