JESSICA SIMPSON’s doing heavy-duty “internal cleansing” – and fiance ERIC JOHNSON’s telling pals that after ingesting her crazy concoctions of maple syrup, lemon juice, beets, herbal laxative tea, cayenne pepper, etc.,

Jess literally stinks up the whole house…and it’s a HUGE house!

Said a friend of the couple: “Eric now insists Jessica must use the guest john only – AND keep lots of matches handy to burn off odors.

It’s gotten so bad that when Jessica’s family and friends visit, they avoid BOTH bathrooms because of the smell – but Jessica’s adamant that she’s got to keep cleansing, in addition to dieting, to speed up the weight-loss process.”