It's when the critters in your body pack their bags and leave. :) What I mean is...
It's the after-effects - it usually happens when one cleanses [which includes a new diet].
May I please inquire what this new diet is?
Salt flushes using Himalayan Crystal Salt would do you wonders - as well as
Liver Flushing and bowel cleansing through means of Okra Pepsin E3 capsules.
parasites DO NOT like salt. They evacuate. I know of an individual who spent many a morning holding his nose and downing his Himalayan salt water drink and he is now in excellent health.
You can pair up this regimen with some Angstrom Minerals.
The liver will deal with the parasites. Your body naturally rids itself of them if you are in good health.
The liver also determines the state of your gastrointestinal tract.
Lapis knows of some herbs that aid greatly to have a dynamic liver flush.
Also, you can begin consuming malic acid [in the form of a tincture, or even freshly-squeezed apple juice] and turmeric to break up any stones you may have.
Education and determination is key.