Here is a post I made about why sometimes a severe infection can sometimes need more than one cleanse:

""No effect = no internal battle = no outward healing crisis (cold sore).

A person with a lower number of "nasties" might have a die-off reaction, but then the ill will go away and not come back. A person with a higher number will have die-off, but the ill will come back - although not as strong - the next cleanses will continue to lower the numbers until they are all gone.

An X amount of an herb will only contain an X amount of the healing chemical componant. This X amount is able to remove XXX amount of "nasties" - while a larger amount of the same herb will remove XXXXXXXX amount of that same "nasty".

It is the exact same principle as modern drug dosage - herbs also carry the same dangers of overdose. The slow action of herbs are part of the reason why modern drugs came into being. For example - it is much quicker for a nursing mother to take a "dry up" shot to stop milk production than it is for her to take large doses of sage for a week.""

This is why some people need more than one parasite cleanse during the first year or so to get parasite free. Some folks can knock out their parasites in one 30 day round while others need to cleanse every 90 days for a while. Overdoing the parasite killing herbs will do more harm than good - your liver has to process ALL chemicals you put into your body - including the herbal ones. I know it is hard to be patient when you KNOW you are hosting parasites - you want them OUT NOW! Herbal treatments are just slower to work - but, in my opinion, they are much more gentle on the body than any fast-acting modern drug.