My ND said it's from the toxins being stirred up and eventually purged. All I know is, it's so bad I can't have anyone over and so forth. It only started after I started the cleanse (Perfect 7). I'm tolerating it fine in every other way. It makes it very hard to run errands, go out to eat if need be, etc. I'm drinking Dandelion Tea also to help detox as well. I need a social life and this is preventing it!