you might be right - oregano oil could be too strong. my dentist (who believes in natural dentistry) recommended i use 10 drops of oregano oil.
what i do if i am swishing for a double session (each about 15/20 minutes- in the first session, i use oregano oil and in the second session -cayenne pepper (5-7 drops). or the other way around. i do not think it makes a difference to me, which goes first.
if i swish longer for a longer time- i just do not add any extras. i just use vco plain.