This mystery has been plaguing me for over a year. It seems to coincide with when I transition back into the LCHF diet. It makes me think it must be related to metabolic processes in some way, but I can't seem to find any literature about it. It's so weird! I'm the only one who can smell this mystery butter, and I smell it all day long. It's as if someone rubbed butter in my nose! It's been over 24 hours since I've consumed butter, and it was a small amount with a fried egg for breakfast. If anyone has access to medical literature and could look this up, I would be most grateful.